equals method behavior of Float

[reji singh]

Hi All,

As per JDK docs

If f1 represents +0.0f while f2 represents -0.0f, or vice versa, the equal test has the value false, //1

even though 0.0f==-0.0f has the value true. //2

Doubt: I agree with statement 1 as -0.0f is not equal to 0.0f but why statement 2 is true? It should not be true as per equality of Objects and primitives.


Thanks

[Henry Wong]

Doubt: I agree with statement 1 as -0.0f is not equal to 0.0f but why statement 2 is true? It should not be true as per equality of Objects and primitives.

Statement 2 is true because that is how it is defined by the IEEE spec. In a comparison, negative zero is equal to positive zero.


As for why statement 1 is false, meaning why it violates IEEE specs -- this was done so maps and sets don't consider positive and negative zero as duplicates of each other.

Henry

[Tom Kowalski]

And don't forget that result depends on whether the variables are Float or float.

  
		Float f1 = -0.0f;
		Float f2 = +0.0f;
		System.out.println(f1 == f2); // This is false
		System.out.println(0.0f == -0.0f);	// This is true

[reji singh]

Thanks Henry and Tomasz