string/stringBuffer(equals method)

[srijan sharma]

hi all,
the folowing code

StringBuffer strlit=new StringBuffer("scjp");
StringBuffer strobj=new StringBuffer("scjp");
System.out.println(strlit.hashCode()==strobj.hashCode());
System.out.println(strlit==strobj);
System.out.println(strlit.equals(strobj));
gives output
false
false
false
but when we use string class
String strlit="scjp";
String strobj=new String("scjp");
System.out.println(strlit.hashCode()==strobj.hashCode())
;
System.out.println(strlit==strobj);
System.out.println(strlit.equals(strobj));
it gives
true
false
true
can somebody explain why equals is not giving true for StringBuffer as the contents are still same i.e. scjp

regards
srijan

[Val Dra]

That's because stringbuffer did not override equals method it uses the default one provided by the Object.

[srijan sharma]

hi,
thanks for the answer. but i could not get the point (overriding concept here). does equals method behave differently for strings and sbuffers.
regads
srijan

[Peter den Haan]

No, StringBuffer.equals() does not behave in the same way as String.equals(). In the javadoc for StringBuffer, you can see that it just inherits the default implementation (Object.equals()), and The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any reference values x and y, this method returns true if and only if x and y refer to the same object (x==y has the value true).
In other words, two stringBuffer1.equals(stringBuffer2) only if stringBuffer1 == stringBuffer2. If you need to compare, sort, convert or otherwise process a StringBuffer, turn it into a String first.
- Peter

[This message has been edited by Peter den Haan (edited February 24, 2001).]