Confusion with equal method

Question

Whenever I use equals() method with two different StringBuffer objects, I get the result as false, but when I use equals() method with two different String objects, I get the result as true. Why?

    String s=new String("434");
    String s1=new String("434");

    System.out.println(s.equals(s1));//true

   StringBuffer s=new StringBuffer("434");
   StringBuffer s1=new StringBuffer("434");

   System.out.println(s.equals(s1));//false

Answer 1

StringBuffer does not override equals(). As such, Object.equals() is called, which compare the object identity (the memory address). String does override equals and compare the content.

Answer 2

StringBuffer does not override Object#equals(), so you're experiencing reference identity-based checks rather than value-based checks. As these StringBuilder instances are distinct, each with different memory locations, the base Object#equals() implementation will always return false.

Here's the definition as of Java 6:

public boolean equals(Object obj) {
  return (this == obj);
}

See the problem?