How does the toString(), ==, equals() object methods work differently or similarly on reference and primitive types?

Question

How does the toString() method, == operator, and equals() method work differently or similarly on reference and primitive types?

Answer 1

For reference types, == will compare the actual reference (where in memory the object resides) where as the equals method performs a comparison of the data.

The JVM will sometimes "String intern" your immutable strings for performance reasons. Causing this:

String a = "abc";
String b = "abc";
if (a == b){ 
    //The if statement will evaluate to true, 
    //if your JVM string interns a and b, 
    //otherwise, it evaluates to false. 
}

http://en.wikipedia.org/wiki/String_interning