explain

[Chiranjeevi Kanthraj]

   StringBuffer s1=new StringBuffer("Alonso");
������� StringBuffer s2=new StringBuffer("Alonso");
������� String s3="Alonso";
������� System.out.println(s1==s2);
������� System.out.println(s1.equals(s2));
������� System.out.println(s1.equals(s3));
������� 
 

out put:
false
false
false

why explain me thanks

[ July 03, 2008: Message edited by: Chiru Raj ]
[ July 03, 2008: Message edited by: Chiru Raj ]

[Joanne Neal]

StringBuffer does not override the equals() method and so inherits the one in the Object class. Have a look at the documentation for Object.equals() and the output will make sense.
[ July 03, 2008: Message edited by: Joanne Neal ]

[Chiranjeevi Kanthraj]

thanks Neal

[Carl Pettersson]

Also, the reason the first comparison (s1==s2) returns false is that the == operator will, when used on objects, check if s1 and s2 are the same object. That is, if they are really references to the same memory area.
Had you written like this:

StringBuffer s1=new StringBuffer("Alonso");
s2=s1;

Then s1==s2 would have been true.

[Ulf Dittmer]

All three lines test object equality, not string equality. That's why they're mutually not equal.

Note that StringBuffer does not override the equals method, and thus uses the one inherited from Object (which tests for object equality). The String class, on the other hand, overrides equals to test for string equality.

Something like "s1.toString().equals(s2.toString())" might give you the result you were expecting.

PS: Which, as I now see, is just about what Joanne and Carl said. Oh well.
[ July 03, 2008: Message edited by: Ulf Dittmer ]

[Campbell Ritchie]

Try

s1.toString().equals(s2.toString())

instead. You should get different results.

[Campbell Ritchie]

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