why equals() not overridden in StringBuffer

[Singhal Anuj]

Why java.lang.String overrides equals() method, but java.lang.StringBuffer does not?

[Steven Bell]

String is considered one of the 'Value' classes (not sure if that's my term or if I picked it up somewhere). This includes all the primitive wrapper classes and String. They share some characteristics.

They are all immutible. They all override equals, hashCode, and toString. I think they also have some other common methods.

To my knowledge no other class in the standard API overrides equals. I could be wrong here, but I think that's right.

[Ernest Friedman-Hill]

No, there are plenty of mutable classes that override equals(); all the java.util Collections classes do, for example.

My guess: they forgot, and then left it that way so as not to break existing code. I think having SB override equals() would be perfectly OK.

[Steven Bell]

I stand corrected, thanks.