Use of =+ operator in Java?

Question

I've the following code:

public class Operators {
    public static void main(String[] args) {
        int i =+ 2;
        System.out.println(i);
    }
}

Upon executing I'm getting the following output: 2

So what does =+ operator actually does here?

EDIT:

As some answered, it is assigning +2 to i, consider the following code:

public class Operators {
    public static void main(String[] args) {
        int i =- -2;
        System.out.println(i);
    }
}

So in above case, output should be -2. But I'm getting 2

So I suppose, it is -(-2), which gives 2. Right?

It would probably make better sense if it was written as `i = +2`, which is the same as `i = 2`. But if I said `i = -2` I think it would make more sense... — MadProgrammer, Oct 03 '13 at 05:28
Do you know Javascript? read [What does = +_ mean in JavaScript](http://stackoverflow.com/questions/15129137/what-does-mean-in-javascript) `=+` is interesting in JavaScript. — Grijesh Chauhan, Oct 03 '13 at 05:30
-(-2) is equivalent to +2. For more info you can look here: http://en.wikipedia.org/wiki/Arithmetic — Red Alert, Oct 03 '13 at 05:34
What's going on here?! People are *upvoting* wrong answers, *downvoting* the right answers. — Rahul, Oct 03 '13 at 05:41
It would be easy to asume that using `=+` is a mistake really wanting to use `+=`. Maybe that's why the downvotes. — madth3, Oct 03 '13 at 06:14
This is actually a duplicate of: http://stackoverflow.com/questions/1642028 http://stackoverflow.com/questions/21029174 http://stackoverflow.com/questions/8825840 http://stackoverflow.com/questions/12313423 http://stackoverflow.com/questions/19151388 http://stackoverflow.com/questions/15129137 http://stackoverflow.com/questions/13946938 http://stackoverflow.com/questions/13874179 — nawfal, Jan 10 '14 at 13:30
http://stackoverflow.com/questions/1839006 http://stackoverflow.com/questions/2034848 http://stackoverflow.com/questions/12442916 http://stackoverflow.com/questions/9955885 http://stackoverflow.com/questions/7967066 http://stackoverflow.com/questions/2939023 http://stackoverflow.com/questions/3543669 http://stackoverflow.com/questions/20754582 :) — nawfal, Jan 10 '14 at 13:32

Subhrajyoti Majumder · Accepted Answer · 2013-10-08T12:48:06.653

11

int i =+ 2;

It is positive 2(+2) assignment to variable i. It is more miningful or understandable if your write like -- int i = +2;

One more example -

int i = 2;
i=+3;
System.out.println(i);

It prints 3.

+ Unary plus operator; indicates positive value (numbers are positive without this, however)

More example - http://docs.oracle.com/javase/tutorial/displayCode.html?code=http://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/UnaryDemo.java

edited Oct 08 '13 at 12:48

answered Oct 03 '13 at 05:27

Subhrajyoti Majumder

40,646
13
77
103

Thanks for editing Suresh :) – Subhrajyoti Majumder Oct 03 '13 at 05:30
Yes you are right Gokul – Subhrajyoti Majumder Oct 03 '13 at 06:18
Any comment for downvoting – Subhrajyoti Majumder Oct 03 '13 at 06:18

devnull · Answer 2 · 2013-10-03T05:50:26.377

5

Upon saying:

int i =+ 2;

+ acts as a unary operator.

To elaborate, it sets i to a positive value 2.

EDIT: Your update says:

int i =- -2;

produces 2. Why?

In this case, it implies that i=-(-(2)). Note that using a unary minus operator might produce unexpected results when the value is, say, Integer.MIN_VALUE.

edited Oct 03 '13 at 05:50

answered Oct 03 '13 at 05:26

devnull

118,548
33
236
227

score 3 · Answer 3 · edited Oct 03 '13 at 07:14

3

You are setting i equal to +2, which is what you got. What kind of output are you expecting?

edited Oct 03 '13 at 07:14

borrrden

33,256
8
74
109

answered Oct 03 '13 at 05:26

Red Alert

3,786
2
17
24

1

Why am I being downvoted for a correct answer? Do I really need to explain that +2 means positive 2? – Red Alert Oct 03 '13 at 05:31
The answer needs much more detail to properly be, well, an answer. – Oct 03 '13 at 05:49
"What kind of output are you expecting" is literally toxic. – Kebab Krabby Mar 19 '19 at 17:16

score 3 · Answer 4 · answered Oct 03 '13 at 05:36

I believe what you mean by =+ is really +=.

Your code is assigning the value of +2 (positive 2) to the integer.

For example:

int x =+ 4;
x =+ 8;
Console.WriteLine(x.ToString());
Console.ReadLine();

Will print "8", not 12. This is because you are assigning x to +4 and then +8.

If you are asking about what += does, it is a shorthand to takes the initial variable and add to it.

x += 8

is the same as

x = x + 8

By changing the previous example form =+ to += give us:

int x = 4;
x += 8;
Console.WriteLine(x.ToString());
Console.ReadLine();

Will print "12".

Why the down vote? Answers original question, as well as an explanation of what looks to be a typo. — user2841290, Oct 03 '13 at 05:42

score 1 · Answer 5 · answered Oct 03 '13 at 05:39

Refer to the following image for unary operators.

enter image description here

Here is an exmaple to understand it.

public class UnaryDemo {
    public static void main(String[] args) {
        int x = 10;
        int y = 20;

        int result = +x;

        System.out.println("+x = " + result);

        result = -y;

        System.out.println("-y = " + result);
        }
    }

and the output is

+x = 10
-y = -20

So think the operator as variable = +value rather than variable =+ values. yeah That space makes it more readable.

score 1 · Answer 6 · answered Oct 03 '13 at 05:54

As all others are answered, I want to give the JLS reference.
Answer to your Edit

int i =- -2;

As specified in jls

Unary numeric promotion (§5.6.1) is performed on the operand.
The type of the unary minus expression is the promoted type of the operand.
At run time, the value of the unary minus expression is the arithmetic negation of the promoted value of the operand.

So,

System.out.println(i); //prints 2

For integer values, negation is the same as subtraction from zero.

Note

For floating-point values, negation is not the same as subtraction from zero, because if x is +0.0, then 0.0-x is +0.0, but -x is -0.0.

Unary minus merely inverts the sign of a floating-point number. Special cases of interest:

If the operand is NaN, the result is NaN. (Recall that NaN has no sign (§4.2.3).)
If the operand is an infinity, the result is the infinity of opposite sign.
If the operand is a zero, the result is the zero of opposite sign.

Useful links

Use of =+ operator in Java?

6 Answers6