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The sign of zero

 
Mafalda Alabort
Greenhorn
Posts: 24
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Hi,
I compiled and run this code. It seems that 100.0/-0 s positive and 100.0/-0.0 is negative. So there is a negative zero for doubles but not for ints?. Is there any explanation for this?
<pre>
public class A1{
public static void main(String [] buff){
//double d = 100.0/-0.0; // outputs negative infinity
double d = 100.0/-0; // outputs positive infinity
if(d == Double.NEGATIVE_INFINITY){
System.out.println("NEGATIVE_INFINITY");
}else{
System.out.println("POSITIVE_INFINITY");
}
}
}
</pre>
Thank you very much
 
Bala Arul
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Posts: 29
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Hi,
As an integer -0's binary representation is as same as 0, by taking 2's compliment.
B Arul.
 
huiying li
Ranch Hand
Posts: 68
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You are correct and here is a quote from Java language specification.
http://java.sun.com/docs/books/jls/second_edition/html/typesValues.doc.html#9208
"Positive zero and negative zero compare equal; thus the result of the expression 0.0==-0.0 is true and the result of 0.0>-0.0 is false. But other operations can distinguish positive and negative zero; for example, 1.0/0.0 has the value positive infinity, while the value of 1.0/-0.0 is negative infinity."
You should also read the API documentation for Double class method equal().
Hope this helps.
 
Mafalda Alabort
Greenhorn
Posts: 24
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Thank you Bala and Huiying
 
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