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 perform this conversion   -5  - gt   5  5  - gt  -5

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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

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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

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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

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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

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What about x    -1    Do you really want a library function for this

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You can use Math   int x   Math abs -5

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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

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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

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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

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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

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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

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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

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original    -1   Simple line of code  original is any int you want it to be

[java] Java math function to convert positive int to negative and negative to positive?

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