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equals() method for Byte class

 
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The explanation for public boolean equals(Object obj)method of Byte class in Java API Website is:......
Returns: true if the objects are the same; false otherwise.
but
Byte b1=new Byte((byte)1);
Byte b2=new Byte((byte)1);
boolean b=b1.equals(b2);
System.out.println(b);
output: true.
So is the explanation on Java API Website misleading? The same for the Short class.
 
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It returns true if the objects are the same, not the values of the objects. Since you are creating two new Byte objects, equals returns false.
 
Bin Wang
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Angela,
but it returns true.
 
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isn't the implementation of .equals() up to the authors discretion? equals should be used for a practical comparison of the class in question. Think of the how the string class implements equals - it tests the VALUE, not the reference. I think the only restriction is that an equals() should test that the comparison is against an instance of the same class that the equals() method belongs to.
 
Angela Lamb
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Sorry, I guess I didn't read carefully enough. The API does seem to be misleading in this case.
 
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Sort of depends on what you think that "the same" means.
This is the actual code that is implemented in the Byte method


* Compares this object to the specified object.
*
* @param obj the object to compare with
* @return true if the objects are the same; false otherwise.
*/
public boolean equals(Object obj) {
if ((obj != null) && (obj instanceof Byte)) { return value == ((Byte)obj).byteValue();
}
return false;
}



It is looking to see if the VALUES are the same.

[This message has been edited by Cindy Glass (edited June 04, 2001).]
 
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To me, "the same" as regards Objects means the same Object (i.e., the reference is to the same address in memory). When the API means the same value, it generally is explicit about that -- e.g., check out how the API describes the Boolean equals() method. In the case of Byte/Short, I think the API documentation is misleading.
Bin, I deleted my original post as soon as I posted because I realized I had referenced the wrong class. I guess you checked the thread in the 5 seconds it was actually there.
[This message has been edited by Scott Appleton (edited June 04, 2001).]
 
Bin Wang
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Thanks Cindy and Scott.
The explanation for equals() method of Float class and Double class on the Java API Website is pretty clear. I just don't know why people who create the java API documents didn't explain the equals() method of Byte and Short class the same way. Maybe there are some reasons for that.
Anyway, What I have learned is: for all the six wrapper classes, the equals() method is comparing the values.

 
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