confusion with primitives

[saipavan vallabhaneni]

public class TestClass
{
      public static void main(String[] args) throws Exception
      {
            float a = Float.MIN_VALUE;
            float b = -a;
System.out.println( a+ "   "+b);

int m = Integer.MIN_VALUE;
            int n = -m;
            System.out.println( m+ "   "+n);
    
int x = -1;
int y = -x;
System.out.println(x +" " + y);
           
  }
}    

why are the m and n values same??? though we have assigned a -m to n...

[Himanshu Gupta]

Try so see output of following code. You will get the reason.

  System.out.println("integer max value: " + Integer.MAX_VALUE);  

[saipavan vallabhaneni]

sorry Himanshu,
i didn't understand what you were trying to tell

1.4E-45 -1.4E-45
-2147483648 -2147483648
-1 1
integer max value: 2147483647

Output completed (0 sec consumed)

i got the following output...

  int m = Integer.MIN_VALUE;  //-2147483648  
            int n = -m;                 //2147483648
            System.out.println( m+ "   "+n);  

why is n being assigned a -ve value where we assigned -m to n

[Abhi vijay]

Hi, check compiling this code.

   byte b1 = -128;
byte c1 = (byte)-b1;
System.out.println(c1);
 

I think it will clear your doubt.
The Range of byte is -128 - 127.
So it cannot hold a value -b1 which is +128.

[saipavan vallabhaneni]

thanks himanshu and abhi

i understood now

[Ruben Soto]

The min value of any integer type is represented at the bit level by the fist bit (the sign bit) being one, and the rest of the bits being 0. This means that:

1000...00 // MIN_VALUE
0111...11 // MIN_VALUE 1's complement
1000...00 // MIN_VALUE 1's complement + 1 = MIN_VALUE 2's complement

So MIN_VALUE and -MIN_VALUE are always the same.

The same is obviously not the case of MAX_VALUE and -MAX_VALUE, since the bit patterns capable of representing negative integers is one more than those capable of representing strictly positive integers.

0111...11 // MAX VALUE
1000...00 // MAX VALUE 1's complement
1000...01 // MAX_VALUE 2's complement

In this case, negating MAX_VALUE will give you what you would expect from a mathematical point of view.