In most programs, objects are created and objects are destroyed, depending on the data and on what is being computed. A reference variable sometimes does and sometimes does not refer to an object. You may need a way to erase the reference inside a variable without creating a new reference. You do this by assigning null to the variable.

String a =                // 1. an object is created;
   new String("stringy"); //    variable a refers to it
String b = null;          // 2. variable b refers to no
                          //    object.
String c =                // 3. an object is created
   new String("");        //    (containing no characters)
                          //    variable c refers to it
if (a != null)            // 4. statement true, so
System.out.println(a);    //    the println(a) executes.

if (b != null)            // 5. statement false, so the
System.out.println(b);    //    println(b) is skipped.

if (c != null)            // 6. statement true, so the
System.out.println(c);    //    println(c) executes (but
                          //    it has no characters to
                          //    print).

Run Output:

stringy