A Set in java never allows duplicates, but it takes StringBuffer objects with the same argument. Why?

Question

public static void main(String[] args) {
    HashSet set = new HashSet(); 
    set.add(new StringBuffer(\"abc\"));
    set.add(new StringBuffer(\"abc\")); 
    set.a         


        

Answer 1

Two StringBuffer objects are different objects despite having the same arguments. Therefore HashSet just adds the StringBuffers instead of ignoring duplicates.