Strings and Object References in Java

The String class is used for text manipulation. As you read, you will learn different ways to create Strings, methods to manipulate Strings, the String concatenation operator '+', and about how Strings are immutable.

24. The startswith () Method



Answer:
  • Can an object reference variable exist without referring to an object?
    • Yes, a reference variable can be declared without initialization:
      String myString;
    • Also, a reference can be set to null.
  • Can an object exist without an object reference variable that refers to it?
    • Yes, as seen in the previous example. Such objects are temporary.
The startsWith() Method

    



    
        

        

        

            
                
class PrefixTest
{
  public static void main ( String args[] )
  {
     String burns = "My love is like a red, red rose.";

     if ( burns.startsWith( "My love" ) )
       System.out.println( "Prefix 1 matches." );
     else
       System.out.println( "Prefix 1 fails." );

     if ( burns.startsWith( "my love" ) )
       System.out.println( "Prefix 2 matches." );
     else
       System.out.println( "Prefix 2 fails." );

     if ( burns.startsWith( "  My love" ) )
       System.out.println( "Prefix 3 matches." );
     else
       System.out.println( "Prefix 3 fails." );

     if ( burns.startsWith( "  My love".trim() ) )
       System.out.println( "Prefix 4 matches." );
     else
       System.out.println( "Prefix 4 fails." );
  }
}

            		
        

    







    









    





    

    

    

    

    

        

    

    

        

        

    





    

        

            

            

            

                

            

        

    





Here is another method of the String class:
    public boolean startsWith(String  prefix); 

The startsWith() method tests if one String is the prefix of another. This is frequently needed in programs. (Although this example is too short to show a real-world situation.)
Notice how trim() is used in the last if statement.




    

        

    




Question 24:
What does the program write?