java - Why does StringBuffer/StringBuilder not override equals or hashCode?

Question

Why does StringBuffer/StringBuilder does not override the equals(), hashcode() methods from object?

Please suggest me clear picture that helps the understand the problem...

Answer 1

Because StringBuffer is mutable, and its primary use is for constructing strings. If you want to compare content, call StringBuffer#toString() and compare the returned value.

It is not generally useful to override hashCode() for mutable objects, since modifying such an object that is used as a key in a HashMap could cause the stored value to be "lost."