Ask why StringBuffer not Not Qualified

nanase

class D
{

    public static void main (String [] args)
    {

String s1 = new String ("hello");

String s2 = new String ("hello");

if (s1.equals (s2))

System.out.println ("equal");

else

System.out.println ("not equal");

    }

}

class E
{

    public static void main (String [] args)
    {

StringBuffer sb1 = new StringBuffer ("hello");

StringBuffer sb2 = new StringBuffer ("hello");

if (sb1.equals (sb2))

System.out.println ("equal");

else

System.out.println ("not equal");

    }

}

Class D outputs equal, this is understandable
But why is Class E not equal? What is the mechanism of StringBuffer?

44964869

StringBuffer calls the equals () method of Object, which compares whether it points to the same object, which is the same as ==.

for non-null reference values ​​x and y, this method returns true, if and only if x and y refer to the same object

nanase

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null 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).

Returns true if and only if x and y refer to the same object, understand, thank you44964869.