Two Reference Variables Pointing to One Object.

Here is another example program:

public class EgString5
{
  public static void main ( String[] args )
  {
    String strA;  // reference to the object
    String strB;  // another reference to the object
     
    strA = new String( "The Gingham Dog" );    // Create the only object.  
                                               // Save its reference in strA.
    System.out.println( strA ); 

    strB = strA;     // Copy the reference into strB.

    System.out.println( strB );

    if ( strA == strB )
      System.out.println( "Same info in each reference variable." );  
   }
}

When this program runs, only one object is created (by the new). The unique reference to the object is put into strA. Then the statement

    strB = strA;   // Copy the reference to strB.

copies the reference that is in strA into strB. It does not make a copy of the object!

Or, saying nearly the same thing: making a copy of a reference to an object does not make a copy of the object! The same information is stored in strA and strB. Both variables refer to the same object.

Both strA and strB contain the same reference. So strA == strB evaluates to true.

This is somewhat like giving your phone number to several people: each copy of your phone number is a reference to you, but there is only one you. The == operator is like comparing phone numbers, but not actually using a phone number to make a call.

The program will output:

The Gingham Dog
The Gingham Dog
Same info in each reference variable.

Answer:

Two Reference Variables Pointing to One Object.

QUESTION 17: