StringBuffer and equals()

[Stephen Pride]

Since equals() is a method in Object, StringBuffer inherits it, but it appears it doesn't do anything with it (i.e., override it to make its own implementation). Is this correct? From the books I've seen, the StringBuffer class doesn't list equals() as one of its methods.
Regards,
SP

[Aru]

Yes Stephan u r right. The StringBuffer class does not override the equals method.
So using equals method with a StringBuffer always returns "false"
Aruna.
[This message has been edited by Aru (edited September 21, 2000).]

[Mapraputa Is]

only small correction: StringBuffer's equals method doesn't always return false. Look at this funny example:

class stringBuf
{
     public static void main(String[] args) 
     {     StringBuffer s = new StringBuffer ("abcd");
           if (s.equals(s.append("a")))
              System.out.println("the same"); 
           else
              System.out.println("not the same"); 
     }
}

prints "the same"
BUT

           StringBuffer s = new StringBuffer ("abcd");
           StringBuffer yetAnotherS = new StringBuffer ("abcd");
           if (s.equals(yetAnotherS))
              System.out.println("the same"); 
           else
              System.out.println("not the same"); 

prints "not the same" - directly the opposite to equals method sematics.

[Anonymous]

Mapraputa:
you are right, can you explain that?
I tried
StringBuffer s=new StringBuffer("aaa");
StringBuffer s1=new StringBuffer("bbb");
s.equals(s1) return false....

[Anonymous]

sorry,
the code I tried are:
StringBuffer s=new StringBuffer("aaa");
StringBuffer s1=new StringBuffer("aaa");
s.equals(s1) return false

[scott irwin]

Since StringBuffer doesn't override equals(Object) we get the base behavior 'if (this == obj)' in Object.equals(Object). StringBuffer.equals() CAN return true when you pass the same reference. Since StringBuffer.append() returns 'this', your code returns true.
[CODE]
StringBuffer b1 = new StringBuffer("abc");
StringBuffer b2 = new StringBuffer("abc");
if (b1.equals(b1)); // always true
if (b1.equals(b2)); // always false b2 is not ref to b1
if (b1.equals(b1.append("def"))); // always true ref == ref
b2 = b1;
if (b1.equals(b2)); // now same ref so true!

[Anonymous]

well, it's good info i got that Stringbuffer doesn't provide 'equals' method and it returns TRUE only when both objects refer to same object. I didn't know that before!!
thanks to all
Ashish

[Stephen Pride]

Thanks to all.
Regards,
SP

[Anonymous]

Thank you, Scott!

[paul wheaton]

Gavin,
I need you to take a look at this thread: http://www.javaranch.com/ubb/Forum10/HTML/000180.html
I would have e-mailed you, but when you are unregistered, I don't know your e-mail address.