Equality of Reference Variable Contents

The == operator looks at the contents of two reference variables. If both reference variables contain the same reference, then the result is true. Otherwise the result is false. Since each object has a unique reference, the == operator returns true if two reference variables refer to the same object.

The == operator does NOT look at objects!   It only looks at references (information about where an object is located).

Here is a section from the previous program, with an additional if statement:

    String strA;  // reference to the first object
    String strB;  // reference to the second object
     
    strA   = new String( "The Gingham Dog" );    // create the first object and  
                                                 // save its reference
    System.out.println( strA ); 

    strB   = new String( "The Calico Cat" );     // create the second object and
                                                 // save its reference
    System.out.println( strB );

    if ( strA == strB ) 
      System.out.println( "This will not print.");

Since the reference in strA is different than the reference in strB,

strA == strB

is false. (Look at the picture on the previous page.) The third println() statement will not execute.