6. The Empty String



Answer:
The code "" calls for a literal, which is a
String object. Although the object exists, it 
contains no characters (since there are no 
characters inside "").emptyString
The reference variable c is initialized to a 
reference to this String object. This is most
certainly a different value than null.







The Empty String





    
        

        

        

            
                
class NullDemo1
{
  public static void main (String[] arg)
  {
    String a = "Random Jottings";   // 1.  an object is created; 
                                    //     variable a refers to it
    String b = null;                // 2.  variable b refers to no object.
    String c = "";                  // 3.  an object is created 
                                    //     (containing no characters); 
                                    //     variable c refers to it

    if ( a != null )                // 4.  ( a != null ) is true, so
       System.out.println( a );     // 5.  println( a ) executes.
                                              
    if ( b != null )                // 6.  ( b != null ) is false, so
       System.out.println( b );     // 7.  println( b ) is skipped.

    if ( c != null )                // 8.  ( c != null ) is true, so
       System.out.println( c );     // 9.  println( c ) executes.
                                    //     (but it has no characters to print.) 
  }
}    

            		
        

    




    


    
A String object that contains no characters is still an object. Such an object is called an empty string. It is similar to having a blank sheet of paper (different from having no paper at all). Overlooking this difference
        is one of the classic confusions of computer programming. It will happen to you. It happens to me. To prepare for future confusion, study the program, step-by-step.





    
The System.out.println() method expects a reference to a String object as a parameter. The example program tests that each variable contains a String reference
        before calling println() with it. (If println() gets a null parameter, it prints out "null" which would be OK. But some methods crash if they get a null parameter. Usually you
        should ensure that methods get the data they expect.)








Question 6:
Examine the following code snippet:
    String alpha = new String("Red Rose") ;

alpha = null;

. . .   
    1. Where is an object constructed?    
    2. What becomes of that object?