Why is java allowing this to compile and what is it interpreting multiple + signs as in this case?

Question

Wasn't sure exactly how to word the question, but I noticed something strange while constructing a date. I found that if I construct a date like this

new Date(+ 1)

it compiled just fine, and so did

new Date(+ + + 1)

If I execute the following, the output is 1

public static void main(String[] args) {
    int x = 1;
    System.out.println(+ + + + x);
}

Can anyone explain what it is that the JVM thinks I am doing?

System.out.println(x + + + + + + x); Prints out 2... And System.out.println(x + + + x + + + x); Prints 3... — dbl, Aug 03 '18 at 15:42
`System.out.println(- - - - x);` works, so why shouldn't this? — clabe45, Aug 03 '18 at 15:42

score 12 · Accepted Answer · answered Aug 03 '18 at 15:42

It's the unary operator (+). You can always add a + to a numeral and that will give you the positive value of the number.

Because you're spacing the tokens out in such a fashion, the lexer is not interpreting anything here as incrementation, so you're adding four unary (+) operations to a value 1.

clabe45 · Answer 2 · 2018-08-03T15:45:22.950

4

It's treating it like this:

System.out.println(+ (+ (+ (+ x))));

This is no different than

System.out.println(- (- (- (- x))));

edited Aug 03 '18 at 15:45

answered Aug 03 '18 at 15:43

clabe45

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Why is java allowing this to compile and what is it interpreting multiple + signs as in this case?

2 Answers2