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equals()

Bob Tank
Greenhorn

Joined: Oct 05, 2000
Posts: 9
Question:
Which of these statements are true?
A. If the references x and y denote two different objects, then the experssion x.equals(y) is always false.
B. All array objects have a method named clone.
Answer is B only. Why isn't answer A. true???
Thanks
Noah Carroll
Ranch Hand

Joined: Sep 20, 2000
Posts: 96
x.equals(y); could be false because the equals() method tests the value of the object not the reference.
however, i don't think it would always be false, because if both objects have the same values then it would be true.
Marilyn de Queiroz
Sheriff

Joined: Jul 22, 2000
Posts: 9047
    
  10
For instance:
String String1 = "abc";
String String2 = "abc";
String1.equals(String2) returns true.
Marilyn


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Anonymous
Ranch Hand

Joined: Nov 22, 2008
Posts: 18944
Marilyn,
While your answer is technically correct, I feel it is not the right example in this case because String1==String2will return true also.
Ambrose
Ajith Kallambella
Sheriff

Joined: Mar 17, 2000
Posts: 5782
Bob,
The equals method is defined in the Object class and it does nothing but basic reference comparison. Several subclasses of Object override the equals method to do content based comparison. The examples are the wrapper classes and the String class.
However, there are some derivatives of Object that doesnot override the equals method. One such class is the StringBuffer. If a class (derived from Object ) does not override the equalsmethod, then as per the OO rules, calling equals method on an instance of such a class will call the Object.equals() method.... and you know what happens
Hence the answer A is false!
Hope that helps,
Ajith
[This message has been edited by Ajith Kallambella (edited October 10, 2000).]


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Subramaniam Chidambaram
Greenhorn

Joined: Oct 18, 2000
Posts: 7
Hi,
If i understand correctly.
If the equals() method is not overridden then the objects
equals() method is called which is same as ==
Thanks

------------------
Subbu


Subbu
Marilyn de Queiroz
Sheriff

Joined: Jul 22, 2000
Posts: 9047
    
  10
Yes, Subbu, that is true.
Marilyn
 
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