Java math function to convert positive int to negative and negative to positive?

Question

Is there a Java function to convert a positive int to a negative one and a negative int to a positive one?

I\'m looking for a reverse function to perfor

Answer 1

No such function exists or is possible to write.

The problem is the edge case Integer.MIN_VALUE (-2,147,483,648 = 0x80000000) apply each of the three methods above and you get the same value out. This is due to the representation of integers and the maximum possible integer Integer.MAX_VALUE (-2,147,483,647 = 0x7fffffff) which is one less what -Integer.MIN_VALUE should be.

Answer 2

You can use the minus operator or Math.abs. These work for all negative integers EXCEPT for Integer.MIN_VALUE! If you do 0 - MIN_VALUE the answer is still MIN_VALUE.

Answer 3

Just use the unary minus operator:

int x = 5;
...
x = -x; // Here's the mystery library function - the single character "-"

Java has two minus operators:

• the familiar arithmetic version (eg 0 - x), and
• the unary minus operation (used here), which negates the (single) operand

This compiles and works as expected.

Answer 4

Another method (2's complement):

public int reverse(int x){
    x~=x;
    x++;
    return x;
}

It does a one's complement first (by complementing all the bits) and then adds 1 to x. This method does the job as well.

Note: This method is written in Java, and will be similar to a lot of other languages

Answer 5

In kotlin you can use unaryPlus and unaryMinus

input = input.unaryPlus()

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/unary-plus.html https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/unary-minus.html

Answer 6

We can reverse Java number int or double using this :

int x = 5;
int y = -7;

x = x - (x*2); // reverse to negative
y = y - (y*2); // reverse to positif

Simple algorithm to reverse number :)