Doubt in StirngBuffer

[Srinivasa Raghavan]

Can any one throw some light on why this expression " (sb1.equals(sb2) " evaluates to false in the following piece of code.

  
public class TestStringBuff
{
public static void main(String[] args)
{
StringBuffer sb1 = new StringBuffer("Ranch");
StringBuffer sb2 = new StringBuffer("Ranch");
StringBuffer sb3 = sb1;

System.out.println("sb1 == sb2 " + (sb1 == sb2) );
System.out.println("sb1.equals(sb2) " + (sb1.equals(sb2) )); /// ?????
 
System.out.println("sb3 == sb1 " + (sb1 == sb3) );
System.out.println("sb3.equals(sb1) " + (sb1.equals(sb3) ));

 
}
}

Output :
sb1 == sb2 false
sb1.equals(sb2) false
sb3 == sb1 true
sb3.equals(sb1) true

[Keith Lynn]

In looking at the documentation, StringBuffer doesn't override the equals method from Object which simply determines if two object references point to the same object.

[Divya Mehrotra]

StringBuffer class DOES NOT override the equals() method. Therefore, it uses Object class' equals(), which only checks for equality of the object references. StringBuffer.equals() does not return true even if the two StringBuffer objects have the same contents:

[Srinivasa Raghavan]

Thanks for your replies. i got it.

[siva prakash]

Hi all,

I am getting compiler error when i tried following, can any explain why its happening

 class MyStringBuffer {
 
            public static void main(String[] args) {
 
            
              StringBuffer st1 = new StringBuffer("mystringBuffer");
              StringBuffer st2 = new StringBuffer("mystringBuffer");
              System.out.println("output is : "+ st1==st2) // this line is throwing compile error, is it implies stringBuffer doesn't implement toString()method of Object class 
            }
 

     }   

thanks in advance

Prakash S

[Keith Lynn]

There is confusion because of the precedence of operators.

Change the line to this.

System.out.println("output is : "+ (st1==st2));

[Layne Lund]

Originally posted by siva prakash:
Hi all,

I am getting compiler error when i tried following, can any explain why its happening...

For future reference, you should start your own thread when asking a new question. Also, it is VERY helpful if you post the exact error message that you get. Otherwise, we are only guessing what the problem is. I don't know about others here at the Ranch, but Most of the time, I won't take the time to compile the code you post. (That's assuming that you provide enough code to compile.) So please post your error messages.

Thank you,

Layne