return value of assignment java

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What is the benefit of having the assignment operator return a value?

I'm developing a language which I intend to replace both Javascript and PHP. (I can't see any problem with this. It's not like either of these languages have a large install base.)

One of the things I wanted to change was to turn the assignment operator into an assignment command, removing the ability to make use of the returned value.

I know that this would mean that those one-line functions that C people love so much would no longer work. I figured (with little evidence beyond my personal experience) that the vast majority of times this happened, it was really intended to be comparison operation.

Or is it? Are there any practical uses of the assignment operator's return value that could not be trivially rewritten? (For any language that has such a concept.)

• language-agnostic

• 12 JS and PHP do not have a large "install base"? –  mhr Commented Feb 13, 2014 at 12:33
• 47 @mri I suspect sarcasm. –  Andy Hunt Commented Feb 13, 2014 at 12:41
• 12 The only useful case I can remember is while((x = getValue()) != null) {} . Replacements will be uglier since you'll need to either use break or repeat the x = getValue assignment. –  CodesInChaos Commented Feb 13, 2014 at 13:04
• 12 @mri Ooh no, I hear those two languages are just trivial things without any significant investment at all. Once the few people who insist on using JS see my language, they will switch over to mine and never have to write === again. I'm equally sure the browser makers will immediately roll out an update that includes my language alongside JS. :) –  billpg Commented Feb 13, 2014 at 14:58
• 4 I would suggest to you that if your intention is to enhance an existing language and you intend it to be adopted widely then 100% backwards compatibility with the existing language is good. See TypeScript as an exemplar. If your intention is to provide a better alternative to an existing language then you have a much harder problem. A new language has to solve an existing realistic problem much much better than the existing language in order to pay for the cost of switching. Learning a language is an investment and it needs to pay off. –  Eric Lippert Commented Feb 13, 2014 at 18:57

9 Answers 9

Technically, some syntactic sugar can be worth keeping even if it can trivially be replaced, if it improves readability of some common operation. But assignment-as-expression does not fall under that. The danger of typo-ing it in place of a comparison means it's rarely used (sometimes even prohibited by style guides) and provokes a double take whenever it is used. In other words, the readability benefits are small in number and magnitude.

A look at existing languages that do this may be worthwhile.

• Java and C# keep assignment an expression but remove the pitfall you mention by requiring conditions to evaluate to booleans. This mostly seems to work well, though people occasionally complain that this disallows conditions like if (x) in place of if (x != null) or if (x != 0) depending on the type of x .
• Python makes assignment a proper statement instead of an expression. Proposals for changing this occasionally reach the python-ideas mailing list, but my subjective impression is that this happens more rarely and generates less noise each time compared to other "missing" features like do-while loops, switch statements, multi-line lambdas, etc.

However, Python allows one special case, assigning to multiple names at once: a = b = c . This is considered a statement equivalent to b = c; a = b , and it's occasionally used, so it may be worth adding to your language as well (but I wouldn't sweat it, since this addition should be backwards-compatible).

• 5 +1 for bringing up a = b = c which the other answers do not really bring up. –  Leo Commented Feb 13, 2014 at 15:53
• 6 A third resolution is to use a different symbol for assignment. Pascal uses := for assignment. –  Brian Commented Feb 13, 2014 at 19:08
• 6 @Brian: Indeed, as does C#. = is assignment, == is comparison. –  Marjan Venema Commented Feb 13, 2014 at 19:47
• 3 In C#, something like if (a = true) will throw a C4706 warning ( The test value in a conditional expression was the result of an assignment. ). GCC with C will likewise throw a warning: suggest parentheses around assignment used as truth value [-Wparentheses] . Those warnings can be silenced with an extra set of parentheses, but they are there to encourage explicitly indicating the assignment was intentional. –  Bob Commented Feb 13, 2014 at 22:27
• 2 @delnan Just a somewhat generic comment, but it was sparked by "remove the pitfall you mention by requiring conditions to evaluate to booleans" - a = true does evaluate to a Boolean and is therefore not an error, but it also raises a related warning in C#. –  Bob Commented Feb 13, 2014 at 23:48

Are there any practical uses of the assignment operator's return value that could not be trivially rewritten?

Generally speaking, no. The idea of having the value of an assignment expression be the value that was assigned means that we have an expression which may be used for both its side effect and its value , and that is considered by many to be confusing.

Common usages are typically to make expressions compact:

has the semantics in C# of "convert z to the type of y, assign the converted value to y, the converted value is the value of the expression, convert that to the type of x, assign to x".

But we are already in the realm of impertative side effects in a statement context, so there's really very little compelling benefit to that over

Similarly with

being a shorthand for

Again, in the original code we are using an expression both for its side effects and its value, and we are making a statement that has two side effects instead of one. Both are smelly; try to have one side effect per statement, and use expressions for their values, not for their side effects.

I'm developing a language which I intend to replace both Javascript and PHP.

If you really want to be bold and emphasize that assignment is a statement and not an equality, then my advice is: make it clearly an assignment statement .

There, done. Or

or even better:

Or even better still

There's absolutely no way that any of those are going to be confused with x == 1 .

• 1 Is the world ready for non-ASCII Unicode symbols in programming languages? –  billpg Commented Feb 14, 2014 at 11:25
• As much as I would love what you suggest, one of my goals is that most "well written" JavaScript can be ported over with little or no modification. –  billpg Commented Feb 14, 2014 at 11:44
• 2 @billpg: Is the world ready ? I don't know -- was the world ready for APL in 1964, decades before the invention of Unicode? Here's a program in APL that picks a random permutation of six numbers out of the first 40: x[⍋x←6?40] APL required its own special keyboard, but it was a pretty successful language. –  Eric Lippert Commented Feb 14, 2014 at 15:17
• @billpg: Macintosh Programmer's Workshop used non-ASCII symbols for things like regex tags or redirection of stderr. On the other hand, MPW had the advantage that the Macintosh made it easy to type non-ASCII characters. I must confess some puzzlement as to why the US keyboard driver doesn't provide any decent means of typing any non-ASCII characters. Not only does Alt-number entry require looking up character codes--in many applications it doesn't even work. –  supercat Commented Feb 14, 2014 at 18:20
• Hm, why would one prefer to assign "to the right" like a+b*c --> x ? This looks strange to me. –  Ruslan Commented Aug 21, 2015 at 10:49

Many languages do choose the route of making assignment a statement rather than an expression, including Python:

and Golang:

Other languages don't have assignment, but rather scoped bindings, e.g. OCaml:

However, let is an expression itself.

The advantage of allowing assignment is that we can directly check the return value of a function inside the conditional, e.g. in this Perl snippet:

Perl additionally scopes the declaration to that conditional only, which makes it very useful. It will also warn if you assign inside a conditional without declaring a new variable there – if ($foo = $bar) will warn, if (my $foo = $bar) will not.

Making the assignment in another statement is usually sufficient, but can bring scoping problems:

Golang heavily relies on return values for error checking. It therefore allows a conditional to take an initialization statement:

Other languages use a type system to disallow non-boolean expressions inside a conditional:

Of course that fails when using a function that returns a boolean.

We now have seen different mechanisms to defend against accidental assignment:

• Disallow assignment as an expression
• Use static type checking
• Assignment doesn't exist, we only have let bindings
• Allow an initialization statement, disallow assignment otherwise
• Disallow assignment inside a conditional without declaration

I've ranked them in order of ascending preference – assignments inside expressions can be useful (and it's simple to circumvent Python's problems by having an explicit declaration syntax, and a different named argument syntax). But it's ok to disallow them, as there are many other options to the same effect.

Bug-free code is more important than terse code.

• +1 for "Disallow assignment as an expression". The use-cases for assignment-as-an-expression don't justify the potential for bugs and readability issues. –  poke Commented Feb 14, 2014 at 17:00

You said "I figured (with little evidence beyond my personal experience) that the vast majority of times this happened, it was really intended to be comparison operation."

Why not FIX THE PROBLEM?

Instead of = for assignment and == for equality test, why not use := for assignment and = (or even ==) for equality?

If you want to make it harder for the programmer to mistake assignment for equality, then make it harder.

At the same time, if you REALLY wanted to fix the problem, you would remove the C crock that claimed booleans were just integers with predefined symbolic sugar names. Make them a different type altogether. Then, instead of saying

you force the programmer to write:

The fact is that assignment-as-an-operator is a very useful construct. We didn't eliminate razor blades because some people cut themselves. Instead, King Gillette invented the safety razor.

• 2 (1) := for assignment and = for equality might fix this problem, but at the cost of alienating every programmer who didn't grow up using a small set of non-mainstream languages. (2) Types other than bools being allows in conditions isn't always due to mixing up bools and integers, it's sufficient to give a true/false interpretation to other types. Newer language that aren't afraid to deviate from C have done so for many types other than integers (e.g. Python considers empty collections false). –  user7043 Commented Feb 13, 2014 at 13:38
• 1 And regarding razor blades: Those serve a use case that necessitates sharpness. On the other hand, I'm not convinced programming well requires assigning to variables in the middle of an expression evaluation. If there was a simple, low-tech, safe and cost efficient way to make body hair disappear without sharp edges, I'm sure razor blades would have been displaced or at least made much more rare. –  user7043 Commented Feb 13, 2014 at 13:40
• 1 @delnan: A wise man once said "Make it as simple as possible, but no simpler." If your objective is to eliminate the vast majority of a=b vs. a==b errors, restricting the domain of conditional tests to booleans and eliminating the default type conversion rules for <other>->boolean gets you just about all the way there. At that point, if(a=b){} is only syntactically legal if a and b are both boolean and a is a legal lvalue. –  John R. Strohm Commented Feb 13, 2014 at 15:07
• Making assignment a statement is at least as simple as -- arguably even simpler than -- the changes you propose, and achieves at least as much -- arguably even more (doesn't even permit if (a = b) for lvalue a, boolean a, b). In a language without static typing, it also gives much better error messages (at parse time vs. run time). In addition, preventing "a=b vs. a==b errors" may not be the only relevant objective. For example, I'd also like to permit code like if items: to mean if len(items) != 0 , and that I'd have to give up to restrict conditions to booleans. –  user7043 Commented Feb 13, 2014 at 15:14
• 1 @delnan Pascal is a non-mainstream language? Millions of people learned programming using Pascal (and/or Modula, which derives from Pascal). And Delphi is still commonly used in many countries (maybe not so much in yours). –  jwenting Commented Feb 14, 2014 at 9:39

To actually answer the question, yes there are numerous uses of this although they are slightly niche.

For example in Java:

The alternative without using the embedded assignment requires the ob defined outside the scope of the loop and two separate code locations that call x.next().

It's already been mentioned that you can assign multiple variables in one step.

This sort of thing is the most common use, but creative programmers will always come up with more.

• Would that while loop condition deallocate and create a new ob object with every loop? –  user3932000 Commented May 3, 2017 at 22:33
• @user3932000 In that case probably not, usually x.next() is iterating over something. It is certainly possible that it could though. –  Tim B Commented May 4, 2017 at 8:18
• I can't get the above to compile unless I declare the variable beforehand and remove the declaration from inside. It says Object cannot be resolved to a variable. –  William Jarvis Commented Apr 15, 2021 at 16:42

Since you get to make up all the rules, why now allow assignment to turn a value, and simply not allow assignments inside conditional steps? This gives you the syntactic sugar to make initializations easy, while still preventing a common coding mistake.

In other words, make this legal:

But make this illegal:

• 2 That seems like a rather ad-hoc rule. Making assignment a statement and extending it to allow a = b = c seems more orthogonal, and easier to implement too. These two approach disagree about assignment in expressions ( a + (b = c) ), but you haven't taken sides on those so I assume they don't matter. –  user7043 Commented Feb 13, 2014 at 13:01
• "easy to implement" shouldn't be much of a consideration. You are defining a user interface -- put the needs of the users first. You simply need to ask yourself whether this behavior helps or hinders the user. –  Bryan Oakley Commented Feb 13, 2014 at 13:05
• if you disallow implicit conversion to bool then you don't have to worry about assignment in conditions –  ratchet freak Commented Feb 13, 2014 at 13:08
• Easier to implement was only one of my arguments. What about the rest? From the UI angle, I might add that IMHO incoherent design and ad-hoc exceptions generally hinders the user in grokking and internalising the rules. –  user7043 Commented Feb 13, 2014 at 13:10
• @ratchetfreak you could still have an issue with assigning actual bools –  jk. Commented Feb 13, 2014 at 13:25

By the sounds of it, you are on the path of creating a fairly strict language.

With that in mind, forcing people to write:

instead of:

might seem an improvement to prevent people from doing:

when they meant to do:

but in the end, this kind of errors are easy to detect and warn about whether or not they are legal code.

However, there are situations where doing:

does not mean that

will be true.

If c is actually a function c() then it could return different results each time it is called. (it might also be computationally expensive too...)

Likewise if c is a pointer to memory mapped hardware, then

are both likely to be different, and also may also have electronic effects on the hardware on each read.

There are plenty of other permutations with hardware where you need to be precise about what memory addresses are read from, written to and under specific timing constraints, where doing multiple assignments on the same line is quick, simple and obvious, without the timing risks that temporary variables introduce

• 4 The equivalent to a = b = c isn't a = c; b = c , it's b = c; a = b . This avoids duplication of side effects and also keeps the modification of a and b in the same order. Also, all these hardware-related arguments are kind of stupid: Most languages are not system languages and are neither designed to solve these problems nor are they being used in situations where these problems occur. This goes doubly for a language that attempts to displace JavaScript and/or PHP. –  user7043 Commented Feb 13, 2014 at 13:04
• delnan, the issue wasn't are these contrived examples, they are. The point still stands that they show the kinds of places where writing a=b=c is common, and in the hardware case, considered good practice, as the OP asked for. I'm sure they will be able to consider their relevance to their expected environment –  Michael Shaw Commented Feb 13, 2014 at 13:51
• Looking back, my problem with this answer is not primarily that it focuses on system programming use cases (though that would be bad enough, the way it's written), but that it rests on assuming an incorrect rewriting. The examples aren't examples of places where a=b=c is common/useful, they are examples of places where order and number of side effects must be taken care of. That is entirely independent. Rewrite the chained assignment correctly and both variants are equally correct. –  user7043 Commented Feb 13, 2014 at 13:58
• @delnan: The rvalue is converted to the type of b in one temp, and that is converted to the type of a in another temp. The relative timing of when those values are actually stored is unspecified. From a language-design perspective, I would think it reasonable to require that all lvalues in a multiple-assignment statement have matching type, and possibly to require as well that none of them be volatile. –  supercat Commented Feb 13, 2014 at 19:17

The greatest benefit to my mind of having assignment be an expression is that it allows your grammar to be simpler if one of your goals is that "everything is an expression"--a goal of LISP in particular.

Python does not have this; it has expressions and statements, assignment being a statement. But because Python defines a lambda form as being a single parameterized expression , that means you can't assign variables inside a lambda. This is inconvenient at times, but not a critical issue, and it's about the only downside in my experience to having assignment be a statement in Python.

One way to allow assignment, or rather the effect of assignment, to be an expression without introducing the potential for if(x=1) accidents that C has is to use a LISP-like let construct, such as (let ((x 2) (y 3)) (+ x y)) which might in your language evaluate as 5 . Using let this way need not technically be assignment at all in your language, if you define let as creating a lexical scope. Defined that way, a let construct could be compiled the same way as constructing and calling a nested closure function with arguments.

On the other hand, if you are simply concerned with the if(x=1) case, but want assignment to be an expression as in C, maybe just choosing different tokens will suffice. Assignment: x := 1 or x <- 1 . Comparison: x == 1 . Syntax error: x = 1 .

• 1 let differs from assignment in more ways than technically introducing a new variable in a new scope. For starters, it has no effect on code outside the let 's body, and therefore requires nesting all code (what should use the variable) further, a significant downside in assignment-heavy code. If one was to go down that route, set! would be the better Lisp analogue - completely unlike comparison, yet not requiring nesting or a new scope. –  user7043 Commented Feb 13, 2014 at 21:36
• @delnan: I'd like to see a combination declare-and-assign syntax which would prohibit reassignment but would allow redeclaration, subject to the rules that (1) redeclaration would only be legal for declare-and-assign identifiers, and (2) redeclaration would "undeclare" a variable in all enclosing scopes. Thus, the value of any valid identifier would be whatever was assigned in the previous declaration of that name. That would seem a little nicer than having to add scoping blocks for variables that are only used for a few lines, or having to formulate new names for each temp variable. –  supercat Commented Feb 14, 2014 at 3:08

Indeed. This is nothing new, all the safe subsets of the C language have already made this conclusion.

MISRA-C, CERT-C and so on all ban assignment inside conditions, simply because it is dangerous.

There exists no case where code relying on assignment inside conditions cannot be rewritten.

Furthermore, such standards also warns against writing code that relies on the order of evaluation. Multiple assignments on one single row x=y=z; is such a case. If a row with multiple assignments contains side effects (calling functions, accessing volatile variables etc), you cannot know which side effect that will occur first.

There are no sequence points between the evaluation of the operands. So we cannot know whether the subexpression y gets evaluated before or after z : it is unspecified behavior in C. Thus such code is potentially unreliable, non-portable and non-conformant to the mentioned safe subsets of C.

The solution would have been to replace the code with y=z; x=y; . This adds a sequence point and guarantees the order of evaluation.

So based on all the problems this caused in C, any modern language would do well to both ban assignment inside conditions, as well as multiple assignments on one single row.

Not the answer you're looking for? Browse other questions tagged language-agnostic syntax operators or ask your own question .

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Java Compound Operators

Last updated: March 17, 2024

• Java Operators

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1. Overview

In this tutorial, we’ll have a look at Java compound operators, their types and how Java evaluates them.

We’ll also explain how implicit casting works.

2. Compound Assignment Operators

An assignment operator is a binary operator that assigns the result of the right-hand side to the variable on the left-hand side. The simplest is the “=” assignment operator:

This statement declares a new variable x , assigns x the value of 5 and returns 5 .

Compound Assignment Operators are a shorter way to apply an arithmetic or bitwise operation and to assign the value of the operation to the variable on the left-hand side.

For example, the following two multiplication statements are equivalent, meaning  a and b will have the same value:

It’s important to note that the variable on the left-hand of a compound assignment operator must be already declared. In other words,  compound operators can’t be used to declare a new variable.

Like the “=” assignment operator, compound operators return the assigned result of the expression:

Both x and y will hold the value 3 .

The assignment (x+=2) does two things: first, it adds 2 to the value of the variable x , which becomes  3;  second, it returns the value of the assignment, which is also 3 .

3. Types of Compound Assignment Operators

Java supports 11 compound assignment operators. We can group these into arithmetic and bitwise operators.

Let’s go through the arithmetic operators and the operations they perform:

• Incrementation: +=
• Decrementation: -=
• Multiplication: *=
• Division: /=
• Modulus: %=

Then, we also have the bitwise operators:

• AND, binary: &=
• Exclusive OR, binary: ^=
• Inclusive OR, binary: |=
• Left Shift, binary: <<=
• Right Shift, binary: >>=
• Shift right zero fill: >>>=

Let’s have a look at a few examples of these operations:

As we can see here, the syntax to use these operators is consistent.

4. Evaluation of Compound Assignment Operations

There are two ways Java evaluates the compound operations.

First, when the left-hand operand is not an array, then Java will, in order:

• Verify the operand is a declared variable
• Save the value of the left-hand operand
• Evaluate the right-hand operand
• Perform the binary operation as indicated by the compound operator
• Convert the result of the binary operation to the type of the left-hand variable (implicit casting)
• Assign the converted result to the left-hand variable

Next, when the left-hand operand is an array, the steps to follow are a bit different:

• Verify the array expression on the left-hand side and throw a NullPointerException  or  ArrayIndexOutOfBoundsException if it’s incorrect
• Save the array element in the index
• Check if the array component selected is a primitive type or reference type and then continue with the same steps as the first list, as if the left-hand operand is a variable.

If any step of the evaluation fails, Java doesn’t continue to perform the following steps.

Let’s give some examples related to the evaluation of these operations to an array element:

As we’d expect, this will throw a  NullPointerException .

However, if we assign an initial value to the array:

We would get rid of the NullPointerException, but we’d still get an  ArrayIndexOutOfBoundsException , as the index used is not correct.

If we fix that, the operation will be completed successfully:

Finally, the x variable will be 6 at the end of the assignment.

5. Implicit Casting

One of the reasons compound operators are useful is that not only they provide a shorter way for operations, but also implicitly cast variables.

Formally, a compound assignment expression of the form:

is equivalent to:

E1 – (T)(E1 op E2)

where T is the type of E1 .

Let’s consider the following example:

Let’s review why the last line won’t compile.

Java automatically promotes smaller data types to larger data ones, when they are together in an operation, but will throw an error when trying to convert from larger to smaller types .

So, first,  i will be promoted to long and then the multiplication will give the result 10L. The long result would be assigned to i , which is an int , and this will throw an error.

This could be fixed with an explicit cast:

Java compound assignment operators are perfect in this case because they do an implicit casting:

This statement works just fine, casting the multiplication result to int and assigning the value to the left-hand side variable, i .

6. Conclusion

In this article, we looked at compound operators in Java, giving some examples and different types of them. We explained how Java evaluates these operations.

Finally, we also reviewed implicit casting, one of the reasons these shorthand operators are useful.

As always, all of the code snippets mentioned in this article can be found in our GitHub repository .

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• Table of Contents
• Course Home
• Assignments
• Peer Instruction (Instructor)
• Peer Instruction (Student)
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• Scratch ActiveCode
• Scratch Activecode
• Instructors Guide
• About Runestone
• Report A Problem
• 1.1 Preface
• 1.2 Why Programming? Why Java?
• 1.3 Variables and Data Types
• 1.4 Expressions and Assignment Statements
• 1.5 Compound Assignment Operators
• 1.6 Casting and Ranges of Variables
• 1.7 Java Development Environments (optional)
• 1.8 Unit 1 Summary
• 1.9 Unit 1 Mixed Up Code Practice
• 1.10 Unit 1 Coding Practice
• 1.11 Multiple Choice Exercises
• 1.12 Lesson Workspace
• 1.3. Variables and Data Types" data-toggle="tooltip">
• 1.5. Compound Assignment Operators' data-toggle="tooltip" >

1.4. Expressions and Assignment Statements ¶

In this lesson, you will learn about assignment statements and expressions that contain math operators and variables.

1.4.1. Assignment Statements ¶

Remember that a variable holds a value that can change or vary. Assignment statements initialize or change the value stored in a variable using the assignment operator = . An assignment statement always has a single variable on the left hand side of the = sign. The value of the expression on the right hand side of the = sign (which can contain math operators and other variables) is copied into the memory location of the variable on the left hand side.

Figure 1: Assignment Statement (variable = expression) ¶

Instead of saying equals for the = operator in an assignment statement, say “gets” or “is assigned” to remember that the variable on the left hand side gets or is assigned the value on the right. In the figure above, score is assigned the value of 10 times points (which is another variable) plus 5.

The following video by Dr. Colleen Lewis shows how variables can change values in memory using assignment statements.

As we saw in the video, we can set one variable to a copy of the value of another variable like y = x;. This won’t change the value of the variable that you are copying from.

Click on the Show CodeLens button to step through the code and see how the values of the variables change.

The program is supposed to figure out the total money value given the number of dimes, quarters and nickels. There is an error in the calculation of the total. Fix the error to compute the correct amount.

Calculate and print the total pay given the weekly salary and the number of weeks worked. Use string concatenation with the totalPay variable to produce the output Total Pay = $3000 . Don’t hardcode the number 3000 in your print statement.

Assume you have a package with a given height 3 inches and width 5 inches. If the package is rotated 90 degrees, you should swap the values for the height and width. The code below makes an attempt to swap the values stored in two variables h and w, which represent height and width. Variable h should end up with w’s initial value of 5 and w should get h’s initial value of 3. Unfortunately this code has an error and does not work. Use the CodeLens to step through the code to understand why it fails to swap the values in h and w.

1-4-7: Explain in your own words why the ErrorSwap program code does not swap the values stored in h and w.

Swapping two variables requires a third variable. Before assigning h = w , you need to store the original value of h in the temporary variable. In the mixed up programs below, drag the blocks to the right to put them in the right order.

The following has the correct code that uses a third variable named “temp” to swap the values in h and w.

The code is mixed up and contains one extra block which is not needed in a correct solution. Drag the needed blocks from the left into the correct order on the right, then check your solution. You will be told if any of the blocks are in the wrong order or if you need to remove one or more blocks.

After three incorrect attempts you will be able to use the Help Me button to make the problem easier.

Fix the code below to perform a correct swap of h and w. You need to add a new variable named temp to use for the swap.

1.4.2. Incrementing the value of a variable ¶

If you use a variable to keep score you would probably increment it (add one to the current value) whenever score should go up. You can do this by setting the variable to the current value of the variable plus one (score = score + 1) as shown below. The formula looks a little crazy in math class, but it makes sense in coding because the variable on the left is set to the value of the arithmetic expression on the right. So, the score variable is set to the previous value of score + 1.

Click on the Show CodeLens button to step through the code and see how the score value changes.

1-4-11: What is the value of b after the following code executes?

• It sets the value for the variable on the left to the value from evaluating the right side. What is 5 * 2?
• Correct. 5 * 2 is 10.

1-4-12: What are the values of x, y, and z after the following code executes?

• x = 0, y = 1, z = 2
• These are the initial values in the variable, but the values are changed.
• x = 1, y = 2, z = 3
• x changes to y's initial value, y's value is doubled, and z is set to 3
• x = 2, y = 2, z = 3
• Remember that the equal sign doesn't mean that the two sides are equal. It sets the value for the variable on the left to the value from evaluating the right side.
• x = 1, y = 0, z = 3

1.4.3. Operators ¶

Java uses the standard mathematical operators for addition ( + ), subtraction ( - ), multiplication ( * ), and division ( / ). Arithmetic expressions can be of type int or double. An arithmetic operation that uses two int values will evaluate to an int value. An arithmetic operation that uses at least one double value will evaluate to a double value. (You may have noticed that + was also used to put text together in the input program above – more on this when we talk about strings.)

Java uses the operator == to test if the value on the left is equal to the value on the right and != to test if two items are not equal. Don’t get one equal sign = confused with two equal signs == ! They mean different things in Java. One equal sign is used to assign a value to a variable. Two equal signs are used to test a variable to see if it is a certain value and that returns true or false as you’ll see below. Use == and != only with int values and not doubles because double values are an approximation and 3.3333 will not equal 3.3334 even though they are very close.

Run the code below to see all the operators in action. Do all of those operators do what you expected? What about 2 / 3 ? Isn’t surprising that it prints 0 ? See the note below.

When Java sees you doing integer division (or any operation with integers) it assumes you want an integer result so it throws away anything after the decimal point in the answer, essentially rounding down the answer to a whole number. If you need a double answer, you should make at least one of the values in the expression a double like 2.0.

With division, another thing to watch out for is dividing by 0. An attempt to divide an integer by zero will result in an ArithmeticException error message. Try it in one of the active code windows above.

Operators can be used to create compound expressions with more than one operator. You can either use a literal value which is a fixed value like 2, or variables in them. When compound expressions are evaluated, operator precedence rules are used, so that *, /, and % are done before + and -. However, anything in parentheses is done first. It doesn’t hurt to put in extra parentheses if you are unsure as to what will be done first.

In the example below, try to guess what it will print out and then run it to see if you are right. Remember to consider operator precedence .

1-4-15: Consider the following code segment. Be careful about integer division.

What is printed when the code segment is executed?

• 0.666666666666667
• Don't forget that division and multiplication will be done first due to operator precedence.
• Yes, this is equivalent to (5 + ((a/b)*c) - 1).
• Don't forget that division and multiplication will be done first due to operator precedence, and that an int/int gives an int result where it is rounded down to the nearest int.

1-4-16: Consider the following code segment.

What is the value of the expression?

• Dividing an integer by an integer results in an integer
• Correct. Dividing an integer by an integer results in an integer
• The value 5.5 will be rounded down to 5

1-4-17: Consider the following code segment.

• Correct. Dividing a double by an integer results in a double
• Dividing a double by an integer results in a double

1-4-18: Consider the following code segment.

• Correct. Dividing an integer by an double results in a double
• Dividing an integer by an double results in a double

1.4.4. The Modulo Operator ¶

The percent sign operator ( % ) is the mod (modulo) or remainder operator. The mod operator ( x % y ) returns the remainder after you divide x (first number) by y (second number) so 5 % 2 will return 1 since 2 goes into 5 two times with a remainder of 1. Remember long division when you had to specify how many times one number went into another evenly and the remainder? That remainder is what is returned by the modulo operator.

Figure 2: Long division showing the whole number result and the remainder ¶

In the example below, try to guess what it will print out and then run it to see if you are right.

The result of x % y when x is smaller than y is always x . The value y can’t go into x at all (goes in 0 times), since x is smaller than y , so the result is just x . So if you see 2 % 3 the result is 2 .

1-4-21: What is the result of 158 % 10?

• This would be the result of 158 divided by 10. modulo gives you the remainder.
• modulo gives you the remainder after the division.
• When you divide 158 by 10 you get a remainder of 8.

1-4-22: What is the result of 3 % 8?

• 8 goes into 3 no times so the remainder is 3. The remainder of a smaller number divided by a larger number is always the smaller number!
• This would be the remainder if the question was 8 % 3 but here we are asking for the reminder after we divide 3 by 8.
• What is the remainder after you divide 3 by 8?

1.4.5. FlowCharting ¶

Assume you have 16 pieces of pizza and 5 people. If everyone gets the same number of slices, how many slices does each person get? Are there any leftover pieces?

In industry, a flowchart is used to describe a process through symbols and text. A flowchart usually does not show variable declarations, but it can show assignment statements (drawn as rectangle) and output statements (drawn as rhomboid).

The flowchart in figure 3 shows a process to compute the fair distribution of pizza slices among a number of people. The process relies on integer division to determine slices per person, and the mod operator to determine remaining slices.

Figure 3: Example Flow Chart ¶

A flowchart shows pseudo-code, which is like Java but not exactly the same. Syntactic details like semi-colons are omitted, and input and output is described in abstract terms.

Complete the program based on the process shown in the Figure 3 flowchart. Note the first line of code declares all 4 variables as type int. Add assignment statements and print statements to compute and print the slices per person and leftover slices. Use System.out.println for output.

1.4.6. Storing User Input in Variables ¶

Variables are a powerful abstraction in programming because the same algorithm can be used with different input values saved in variables.

Figure 4: Program input and output ¶

A Java program can ask the user to type in one or more values. The Java class Scanner is used to read from the keyboard input stream, which is referenced by System.in . Normally the keyboard input is typed into a console window, but since this is running in a browser you will type in a small textbox window displayed below the code. The code below shows an example of prompting the user to enter a name and then printing a greeting. The code String name = scan.nextLine() gets the string value you enter as program input and then stores the value in a variable.

Run the program a few times, typing in a different name. The code works for any name: behold, the power of variables!

Run this program to read in a name from the input stream. You can type a different name in the input window shown below the code.

Try stepping through the code with the CodeLens tool to see how the name variable is assigned to the value read by the scanner. You will have to click “Hide CodeLens” and then “Show in CodeLens” to enter a different name for input.

The Scanner class has several useful methods for reading user input. A token is a sequence of characters separated by white space.

Run this program to read in an integer from the input stream. You can type a different integer value in the input window shown below the code.

A rhomboid (slanted rectangle) is used in a flowchart to depict data flowing into and out of a program. The previous flowchart in Figure 3 used a rhomboid to indicate program output. A rhomboid is also used to denote reading a value from the input stream.

Figure 5: Flow Chart Reading User Input ¶

Figure 5 contains an updated version of the pizza calculator process. The first two steps have been altered to initialize the pizzaSlices and numPeople variables by reading two values from the input stream. In Java this will be done using a Scanner object and reading from System.in.

Complete the program based on the process shown in the Figure 5 flowchart. The program should scan two integer values to initialize pizzaSlices and numPeople. Run the program a few times to experiment with different values for input. What happens if you enter 0 for the number of people? The program will bomb due to division by zero! We will see how to prevent this in a later lesson.

The program below reads two integer values from the input stream and attempts to print the sum. Unfortunately there is a problem with the last line of code that prints the sum.

Run the program and look at the result. When the input is 5 and 7 , the output is Sum is 57 . Both of the + operators in the print statement are performing string concatenation. While the first + operator should perform string concatenation, the second + operator should perform addition. You can force the second + operator to perform addition by putting the arithmetic expression in parentheses ( num1 + num2 ) .

More information on using the Scanner class can be found here https://www.w3schools.com/java/java_user_input.asp

1.4.7. Programming Challenge : Dog Years ¶

In this programming challenge, you will calculate your age, and your pet’s age from your birthdates, and your pet’s age in dog years. In the code below, type in the current year, the year you were born, the year your dog or cat was born (if you don’t have one, make one up!) in the variables below. Then write formulas in assignment statements to calculate how old you are, how old your dog or cat is, and how old they are in dog years which is 7 times a human year. Finally, print it all out.

Calculate your age and your pet’s age from the birthdates, and then your pet’s age in dog years. If you want an extra challenge, try reading the values using a Scanner.

1.4.8. Summary ¶

Arithmetic expressions include expressions of type int and double.

The arithmetic operators consist of +, -, * , /, and % (modulo for the remainder in division).

An arithmetic operation that uses two int values will evaluate to an int value. With integer division, any decimal part in the result will be thrown away, essentially rounding down the answer to a whole number.

An arithmetic operation that uses at least one double value will evaluate to a double value.

Operators can be used to construct compound expressions.

During evaluation, operands are associated with operators according to operator precedence to determine how they are grouped. (*, /, % have precedence over + and -, unless parentheses are used to group those.)

An attempt to divide an integer by zero will result in an ArithmeticException to occur.

The assignment operator (=) allows a program to initialize or change the value stored in a variable. The value of the expression on the right is stored in the variable on the left.

During execution, expressions are evaluated to produce a single value.

The value of an expression has a type based on the evaluation of the expression.

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Operators are used to perform operations on variables and values.

In the example below, we use the + operator to add together two values:

Try it Yourself »

Although the + operator is often used to add together two values, like in the example above, it can also be used to add together a variable and a value, or a variable and another variable:

Java divides the operators into the following groups:

• Arithmetic operators
• Assignment operators
• Comparison operators
• Logical operators
• Bitwise operators

Arithmetic Operators

Arithmetic operators are used to perform common mathematical operations.

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Java Assignment Operators

Assignment operators are used to assign values to variables.

In the example below, we use the assignment operator ( = ) to assign the value 10 to a variable called x :

The addition assignment operator ( += ) adds a value to a variable:

A list of all assignment operators:

Java Comparison Operators

Comparison operators are used to compare two values (or variables). This is important in programming, because it helps us to find answers and make decisions.

The return value of a comparison is either true or false . These values are known as Boolean values , and you will learn more about them in the Booleans and If..Else chapter.

In the following example, we use the greater than operator ( > ) to find out if 5 is greater than 3:

Java Logical Operators

You can also test for true or false values with logical operators.

Logical operators are used to determine the logic between variables or values:

Java Bitwise Operators

Bitwise operators are used to perform binary logic with the bits of an integer or long integer.

Note: The Bitwise examples above use 4-bit unsigned examples, but Java uses 32-bit signed integers and 64-bit signed long integers. Because of this, in Java, ~5 will not return 10. It will return -6. ~00000000000000000000000000000101 will return 11111111111111111111111111111010

In Java, 9 >> 1 will not return 12. It will return 4. 00000000000000000000000000001001 >> 1 will return 00000000000000000000000000000100

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Multiply 10 with 5 , and print the result.

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Understand parameters and return values

Since the beginning of this course, we have been using functions (or methods), such as   System.out.println() . In this chapter, you will learn the different components of a method declaration (parameters and return value) and the difference between a value type and a reference type.

What is a method declaration composed of?

Let's say you have a 6 (length) by 4 (width) rectangle and you want to print its perimeter.

This is a correctly implemented method, but let's agree, quite useless as you'll always end up working with the same numbers.

Functions with parameters

To address this limitation, you need to make your function accept the numbers from the outside. This can be done by defining a function with parameters.

In Java, the variable name and type of the parameter are part of function declaration. Here's what it looks like:

Parameters are variables listed in the function declaration that are specified inside  ()  by the name and type. Now you can call this function and pass any values you want to it:

Each value is assigned to a parameter in the order they are defined.

Let's get deeper into the terminology. Parameters are the variables declared in a function. The values passed to that function are called arguments.

This is great, we've added some purpose to our function.

Now, what can we do about the result?

Often, the code that called the function needs an answer to perform its own work. This answer can be provided by the  return value of the function.

Define a return value

To define a return value, you need to:

Alter the  declaration  of the function to indicate that it's expected to return a result.

End the function with the  return keyword.

Here is how to turn the  displayPerimeter  into a  calculatePerimeter  function. This will  return the result of the calculation so that it can be used by the calling function:

You could also forgo the sum variable and return directly the result of the calculation expression:

Once your function is defined, you can use it as many times as you want. Here are a couple of variations:

In the example above, we used the result of the first calculation as a parameter for the next one.

Another thing you need to understand: some variables store a value directly, while others store a reference . This has an impact on how they are sent as  arguments to a function.

Differentiate value types and reference types

You've learned about variables types which can be simple - like numbers or strings, or, more complex, like classes.

Each of those types are classified as either a value type  or a reference type. 

Let's start with the value type.

Value types

Let's use integers as an example. If you create an integer variable and then assign it to another variable, the value of the first variable will be copied to the second one:

  Since  int  is a value type, b is assigned a copy of the value of a. That means that if you later change the value of   a  , the value of   b  will not be changed.

  That's pretty straightforward. Next comes reference types.

Reference types

We'll work with classes in this section. When you create a variable and assign an instance of class to it, the object gets created, but the variable itself holds a  reference  to that object:  the location of where it's stored in the memory. Then, when you assign the value of that variable to another variable, the object itself will not be copied, and the new variable will hold a reference to it - the same address.

  Here's an example:

  If you want to paint the car which is accessible by the second variable, the first variable will be also affected as both point to the exact same instance of the car class:

  See the difference? ⚡️This is very useful as it saves lots of memory space when you need to pass around the same object along your program. However, this can also be dangerous as changing an object in one part of the program will affect all other parts of the program working with the same object.

This is something you'll need to pay attention to with parameters of functions. When you pass reference types as parameters, all modifications you perform on them within those functions modify the original objects:

Hmm...how about parameters of the functions being constants in Java? Parameters of a function in Java are indeed constants and cannot be modified, which means you cannot assign a new value to the whole new object (or, a reference to an object). But you CAN modify attributes of that object, which is exactly what we did in the example above.

Lot's of new knowledge here, you are progressing so fast!

In this chapter, you've learned:

Functions can have  parameters  and  return values.

A return value is a result of the function's execution. It can be returned to the block of code that called the function and then used as needed.

Parameters are the input for a function that are necessary for the it to be executed and produce a result.

Parameters are variables defined by name and type. They are  specified in the function's declaration.

When calling a function, you are passing values to those variables. Those values are called  arguments.

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1.7 Java | Assignment Statements & Expressions

An assignment statement designates a value for a variable. An assignment statement can be used as an expression in Java.

After a variable is declared, you can assign a value to it by using an assignment statement . In Java, the equal sign = is used as the assignment operator . The syntax for assignment statements is as follows:

An expression represents a computation involving values, variables, and operators that, when taking them together, evaluates to a value. For example, consider the following code:

You can use a variable in an expression. A variable can also be used on both sides of the =  operator. For example:

In the above assignment statement, the result of x + 1  is assigned to the variable x . Let’s say that x is 1 before the statement is executed, and so becomes 2 after the statement execution.

To assign a value to a variable, you must place the variable name to the left of the assignment operator. Thus the following statement is wrong:

Note that the math equation  x = 2 * x + 1  ≠ the Java expression x = 2 * x + 1

Which is equivalent to:

And this statement

is equivalent to:

Note: The data type of a variable on the left must be compatible with the data type of a value on the right. For example, int x = 1.0 would be illegal, because the data type of x is int (integer) and does not accept the double value 1.0 without Type Casting .

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The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available. See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases. See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.

Returning a Value from a Method

A method returns to the code that invoked it when it

• completes all the statements in the method,
• reaches a return statement, or
• throws an exception (covered later),

whichever occurs first.

You declare a method's return type in its method declaration. Within the body of the method, you use the return statement to return the value.

Any method declared void doesn't return a value. It does not need to contain a return statement, but it may do so. In such a case, a return statement can be used to branch out of a control flow block and exit the method and is simply used like this:

If you try to return a value from a method that is declared void , you will get a compiler error.

Any method that is not declared void must contain a return statement with a corresponding return value, like this:

The data type of the return value must match the method's declared return type; you can't return an integer value from a method declared to return a boolean.

The getArea() method in the Rectangle Rectangle class that was discussed in the sections on objects returns an integer:

This method returns the integer that the expression width*height evaluates to.

The getArea method returns a primitive type. A method can also return a reference type. For example, in a program to manipulate Bicycle objects, we might have a method like this:

Returning a Class or Interface

If this section confuses you, skip it and return to it after you have finished the lesson on interfaces and inheritance.

When a method uses a class name as its return type, such as whosFastest does, the class of the type of the returned object must be either a subclass of, or the exact class of, the return type. Suppose that you have a class hierarchy in which ImaginaryNumber is a subclass of java.lang.Number , which is in turn a subclass of Object , as illustrated in the following figure .

The class hierarchy for ImaginaryNumber

Now suppose that you have a method declared to return a Number :

The returnANumber method can return an ImaginaryNumber but not an Object . ImaginaryNumber is a Number because it's a subclass of Number . However, an Object is not necessarily a Number — it could be a String or another type.

You can override a method and define it to return a subclass of the original method, like this:

This technique, called covariant return type , means that the return type is allowed to vary in the same direction as the subclass.

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Programming in Java | Week 1

Session: JULY-AUG 2024

Course name: Programming In Java

Course Link: Click Here

For answers or latest updates join our telegram channel: Click here to join

These are Programming In Java Week 1 Assignment 1 Nptel Answers

Q1.Which of the following is not a valid comment in Java? a. /** comment * / b. /* comment * / c. / *comment / d. // comment

Answer: c. / *comment /

Q2.What is the output of the following code? a. NPTEL2024 44java b. NPTEL44 44java c. NPTEL2024 2024java d. NPTEL44 2024java

Answer: a. NPTEL202444java

Q3.Which of the following is used to find and fix bugs in the Java programs? a. JVM b. JRE c. JDK d. JDB

Answer: d. JDB

Q4.What is the value returned by the method f() defined below? public static int f(int x, int y){return (x>y) ? y : x;} a. The sum of x and y, that is, x + y. b. The difference of x and y, that is, x – y. c. The maximum of x and y, that is, the larger value of x and y. d. The minimum of x and y, that is, the smaller value of x and y.

Answer: d. The minimum of x and y, that is, the smaller value of x and y.

Q5.Consider the following program. What will be the output of the program if it is executed? a. Print first six even numbers. b. Print first six odd numbers. c. Print first six prime numbers. d. Print first six Fibonacci numbers.

Answer: d. Print first six Fibonacci numbers.

Q6. Which program is used to compile Java source code into bytecode? a. javap b. javac c. java d. javad

Answer: b. javac

Q7. Consider the following program. a. 50 b. 10 c. Compiler error d. 5

Answer:a. 50

Q8. What is the incorrect statement about bytecode? a. Java when compiles the source code, it converts it to bytecode. b. JVM (Java Virtual Machine) is an interpreter of bytecode. c. Bytecode is not portable and it needs to be compiled separately for each platform. d. JVM offers a protected environment which helps in enhanced safety for the system.

Answer:c. Bytecode is not portable and it needs to be compiled separately for each platform.

Q9. In Java, what is the role of the public static void main(String[] args) method? a. Initialization method b. Execution entry point c. Constructor d. Destructor

Answer: b. Execution entry point

Q10. What is the purpose of the break statement in Java? a. To terminate the program b. To exit a loop or switch statement c. To skip the next iteration of a loop d. To return a value from a method

Answer: b. To exit a loop or switch statement

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Overview of Java

• Introduction to Java
• The Complete History of Java Programming Language
• C++ vs Java vs Python
• How to Download and Install Java for 64 bit machine?
• Setting up the environment in Java
• How to Download and Install Eclipse on Windows?
• JDK in Java
• How JVM Works - JVM Architecture?
• Differences between JDK, JRE and JVM
• Just In Time Compiler
• Difference between JIT and JVM in Java
• Difference between Byte Code and Machine Code
• How is Java platform independent?

Basics of Java

• Java Basic Syntax
• Java Hello World Program
• Java Data Types
• Primitive data type vs. Object data type in Java with Examples
• Java Identifiers

Operators in Java

• Java Variables
• Scope of Variables In Java

Wrapper Classes in Java

Input/output in java.

• How to Take Input From User in Java?
• Scanner Class in Java
• Java.io.BufferedReader Class in Java
• Difference Between Scanner and BufferedReader Class in Java
• Ways to read input from console in Java
• System.out.println in Java
• Difference between print() and println() in Java
• Formatted Output in Java using printf()
• Fast I/O in Java in Competitive Programming

Flow Control in Java

• Decision Making in Java (if, if-else, switch, break, continue, jump)
• Java if statement with Examples
• Java if-else
• Java if-else-if ladder with Examples
• Loops in Java
• For Loop in Java
• Java while loop with Examples
• Java do-while loop with Examples
• For-each loop in Java
• Continue Statement in Java
• Break statement in Java
• Usage of Break keyword in Java
• return keyword in Java
• Java Arithmetic Operators with Examples
• Java Unary Operator with Examples
• Java Assignment Operators with Examples
• Java Relational Operators with Examples
• Java Logical Operators with Examples

Java Ternary Operator with Examples

• Bitwise Operators in Java
• Strings in Java
• String class in Java
• Java.lang.String class in Java | Set 2
• Why Java Strings are Immutable?
• StringBuffer class in Java
• StringBuilder Class in Java with Examples
• String vs StringBuilder vs StringBuffer in Java
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• StringTokenizer Methods in Java with Examples | Set 2
• StringJoiner Class in Java
• Arrays in Java
• Arrays class in Java
• Multidimensional Arrays in Java
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OOPS in Java

• Object Oriented Programming (OOPs) Concept in Java
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• Classes and Objects in Java
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• Java Methods

Access Modifiers in Java

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Abstraction in java, encapsulation in java, polymorphism in java, interfaces in java.

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• abstract keyword in java
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Constructors in Java

• Copy Constructor in Java
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• Private Constructors and Singleton Classes in Java

Methods in Java

• Static methods vs Instance methods in Java
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Keywords in Java

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Memory Allocation in Java

• Java Memory Management
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• Garbage Collection in Java
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Classes of Java

• Understanding Classes and Objects in Java
• Singleton Method Design Pattern in Java
• Object Class in Java
• Inner Class in Java
• Throwable Class in Java with Examples

Packages in Java

• Packages In Java
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• Java.util Package in Java
• Java.lang package in Java
• Java.io Package in Java
• Java Collection Tutorial

Exception Handling in Java

• Exceptions in Java
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• Checked vs Unchecked Exceptions in Java
• Java Try Catch Block
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• throw and throws in Java
• User-defined Custom Exception in Java
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• Multithreading in Java
• Lifecycle and States of a Thread in Java
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• What does start() function do in multithreading in Java?
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• Thread.sleep() Method in Java With Examples
• Synchronization in Java
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• Lock framework vs Thread synchronization in Java
• Difference Between Atomic, Volatile and Synchronized in Java
• Deadlock in Java Multithreading
• Deadlock Prevention And Avoidance
• Difference Between Lock and Monitor in Java Concurrency
• Reentrant Lock in Java

File Handling in Java

• Java.io.File Class in Java
• Java Program to Create a New File
• Different ways of Reading a text file in Java
• Java Program to Write into a File
• Delete a File Using Java
• File Permissions in Java
• FileWriter Class in Java
• Java.io.FileDescriptor in Java
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• Regular Expressions in Java
• Regex Tutorial - How to write Regular Expressions?
• Matcher pattern() method in Java with Examples
• Pattern pattern() method in Java with Examples
• Quantifiers in Java
• java.lang.Character class methods | Set 1
• Java IO : Input-output in Java with Examples
• Java.io.Reader class in Java
• Java.io.Writer Class in Java
• Java.io.FileInputStream Class in Java
• FileOutputStream in Java
• Java.io.BufferedOutputStream class in Java
• Java Networking
• TCP/IP Model
• User Datagram Protocol (UDP)
• Difference Between IPv4 and IPv6
• Difference between Connection-oriented and Connection-less Services
• Socket Programming in Java
• java.net.ServerSocket Class in Java
• URL Class in Java with Examples

JDBC - Java Database Connectivity

• Introduction to JDBC (Java Database Connectivity)
• JDBC Drivers
• Establishing JDBC Connection in Java
• Types of Statements in JDBC
• JDBC Tutorial
• Java 8 Features - Complete Tutorial

Operators constitute the basic building block of any programming language. Java provides many types of operators that can be used according to the need to perform various calculations and functions, be it logical, arithmetic, relational, etc. They are classified based on the functionality they provide. Here are a few types: 

• Arithmetic Operators
• Unary Operators
• Assignment Operator
• Relational Operators
• Logical Operators
• Ternary Operator
• Bitwise Operators
• Shift Operators

This article explains all that one needs to know regarding Ternary Operators. 

Ternary Operator in Java

Java ternary operator is the only conditional operator that takes three operands. It’s a one-liner replacement for the if-then-else statement and is used a lot in Java programming. We can use the ternary operator in place of if-else conditions or even switch conditions using nested ternary operators. Although it follows the same algorithm as of if-else statement, the conditional operator takes less space and helps to write the if-else statements in the shortest way possible.

If operates similarly to that of the if-else statement as in Exression2 is executed if Expression1 is true else Expression3 is executed.  

Example:   

Flowchart of Ternary Operation  

Examples of Ternary Operators in Java

Example 1:  .

Below is the implementation of the Ternary Operator:

Complexity of the above method:

Time Complexity: O(1) Auxiliary Space: O(1)

Example 2:  

Below is the implementation of the above method:

Implementing ternary operator on Boolean values:

Explanation of the above method:

In this program, a Boolean variable condition is declared and assigned the value true. Then, the ternary operator is used to determine the value of the result string. If the condition is true, the value of result will be “True”, otherwise it will be “False”. Finally, the value of result is printed to the console.

Advantages of Java Ternary Operator

• Compactness : The ternary operator allows you to write simple if-else statements in a much more concise way, making the code easier to read and maintain.
• Improved readability : When used correctly, the ternary operator can make the code more readable by making it easier to understand the intent behind the code.
• Increased performance: Since the ternary operator evaluates a single expression instead of executing an entire block of code, it can be faster than an equivalent if-else statement.
• Simplification of nested if-else statements: The ternary operator can simplify complex logic by providing a clean and concise way to perform conditional assignments.
• Easy to debug : If a problem occurs with the code, the ternary operator can make it easier to identify the cause of the problem because it reduces the amount of code that needs to be examined.

It’s worth noting that the ternary operator is not a replacement for all if-else statements. For complex conditions or logic, it’s usually better to use an if-else statement to avoid making the code more difficult to understand.

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How to generate return value type and variable assignment in Eclipse java editor?

If I have a statement like this " EntitiesProvider.getEntities();

Any idea how to "generate" the assignment to variable of return Type ?

so that this would be generated Map<String, Entity> hashMap =

this is the result :

It is similar to ctrl + 1 and Change type, if it returns different Type that you already have there.

I find myself doing myself manually very often...

4 Answers 4

Ctrl+2, L is one option, and the other is Alt+Shift+L when the desired statement is selected. The popup will appear allowing to set variable name & few additional options (e.g., "Replace occurrences of the selected expression with references to the local variable").

I prefer Alt+Shift+L because it allows marking specific part of the line for variable extraction.

.. and here's a simple example:

You can select the whole line to assign it to FileInputStream variable, or you can 'extract' new File("test.txt") , or even String expression "test.txt" .

P.S. Sometimes I wish it would be able to let me choose supertype from combo box in a pop-up, e.g. InputStream in this specific example.

CTRL=2,L will do what you are looking for.

What is wrong with Ctrl + 2 , L . With Tab and ↓ / ↑ ?

• 2 CTRL+SHIFT+L brings a popup for all other Shortcuts, if you sometime search for another. –  oliholz Commented Aug 17, 2011 at 14:27

CTRL+2,L and ALT+CTRL+L can get the job done for you.

CTRL+2 is a short key to a quick assist tool which can perform

• assigning to a F ield (F)
• assigning to a L ocal variable (L)
• extracting M ethod (M)
• R enaming in file (R)

you can press any key of these four as u need it.

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