Even I am not sure why it returns false, but I have come across the API documentation of the equals method defined in the object class and it says that if and only if x and y refers to the same object, only then it returns true.
The following quote is the documentation of the equals method defined in the Object class.
equals public boolean equals(Object obj)Indicates whether some other object is "equal to" this one. The equals method implements an equivalence relation on non-null object references:
It is reflexive: for any non-null reference value x, x.equals(x) should return true. It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true. It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true. It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified. For any non-null reference value x, x.equals(null) should return false. 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).
Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.
Parameters: obj - the reference object with which to compare. Returns: true if this object is the same as the obj argument; false otherwise. See Also: hashCode(), Hashtable
Please if someone put a little more light on this.
The StringBuffer.equals method does not override Object.equals. The StringBuffer.equals method compares the reference values--not the contents of the StringBuffer instances. Since the reference values sb1 and sb2 are different, the method invocation expression sb1.equals(sb2) produces the value false.