confusion on (==)

[Karu Raj]

public void check()
2: {
3: System.out.println(Math.min(-0.0,+0.0));
4: System.out.println(Math.max(-0.0,+0.0));
5: System.out.println(Math.min(-0.0,+0.0) == Math.max(0.0,+0.0));
6: }

A) prints -0.0, +0.0 and false.
B) prints -0.0, +0.0 and true.
C) prints 0.0, 0.0 and false.
D) prints 0.0, 0.0 and true.

The answer is B why please explain

[Sandeep Chhabra]

hi,
as far as i think comparing -0.0 ==0.0 always returns true.
coz actually there is nothing like -0.0 and +0.0, both are just 0 and thus the equality test succeeds.

Sandy

[marc weber]

If you check the API for the min and max methods that take floating-point primitives, you will find...

Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero.

Note that == is a "numerical comparison operator."
[ September 14, 2005: Message edited by: marc weber ]

[Roopesh Gulecha]

Actually for floating point numbers in Java, -0.0 and 0.0 are different.
Math.min(-0.0,0.0) outputs -0.0, but
-0.0 == 0.0 is true too..So it is a little wierd, but that is how it is.
The floating point numbers (double and float) are in this order
NEGATIVE_INFINITY --> negative integers/fractions --> -0.0 --> 0.0 --> positive integers/fractions --> POSITIVE_INFINITY
This is what I know.

Roopesh.

[marc weber]

Originally posted by Roopesh Gulecha:
... The floating point numbers (double and float) are in this order
NEGATIVE_INFINITY --> negative integers/fractions --> -0.0 --> 0.0 --> positive integers/fractions --> POSITIVE_INFINITY...

Well, the "order" of signed zeros depends on the context. Within the min and max methods of Math, this order exists. However, numerical comparison operators like > and < will not recognize an order.

[marc weber]

For example...

class Zeros {
  public static void main(String[] args) {
    //ORDERED IN THIS CONTEXT...
    System.out.println("min: " + Math.min(-0.0, +0.0));
    System.out.println("max: " + Math.max(-0.0, +0.0));
 
    //EQUAL IN THIS CONTEXT...
    System.out.println("-0.0 < +0.0: " + (-0.0 < +0.0));
    System.out.println("-0.0 > +0.0: " + (-0.0 > +0.0));
  }
}

[Pulamathi Pavan Kumar]

Hi,

It is mentioned in JLS that in Floating point numbers -0.0 and +0.0 are considered equal when "==" operator is used. Hence true is the answer.
If any thing is to be changed in the answer for perfection, please let me know.

Regards,
Pavan.