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:
0 - x
), andThis compiles and works as expected.
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 :)
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.
original *= -1;
Simple line of code, original is any int you want it to be.
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
The easiest thing to do is 0- the value
for instance if int i = 5;
0-i would give you -5
and if i was -6;
0- i would give you 6
Necromancing here.
Obviously, x *= -1;
is far too simple.
Instead, we could use a trivial binary complement:
number = ~(number - 1) ;
Like this:
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
public static void main (String[] args) throws java.lang.Exception
{
int iPositive = 15;
int iNegative = ( ~(iPositive - 1) ) ; // Use extra brackets when using as C preprocessor directive ! ! !...
System.out.println(iNegative);
iPositive = ~(iNegative - 1) ;
System.out.println(iPositive);
iNegative = 0;
iPositive = ~(iNegative - 1);
System.out.println(iPositive);
}
}
That way we can ensure that mediocre programmers don't understand what's going on ;)
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.
You can use Math:
int x = Math.abs(-5);
Yes, as was already noted by Jeffrey Bosboom (Sorry Jeffrey, I hadn't noticed your comment when I answered), there is such a function: Math.negateExact.
and
No, you probably shouldn't be using it. Not unless you need a method reference.
x = -x;
This is probably the most trivial question I have ever seen anywhere.
... and why you would call this trivial function 'reverse()' is another mystery.
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
Source: Stackoverflow.com