1	// Example 7.1 joi/examples/RumpelStiltskinDemo.java
     2	//
     3	// 
     4	// Copyright 2003 Bill Campbell and Ethan Bolker
     5	
     6	// Practice with simple exceptions - some from the API, one declared here.
     7	
     8	public class RumpelStiltskinDemo 
     9	{
    10	    public static void main( String[] args ) 
    11	    {
    12	        Wizard rumpelstiltskin = new Wizard("RumpelStiltskin");
    13	        Wizard aNullWizard     = null;
    14	
    15	        // see if the first command line argument ( args[0] )
    16	        // is the right name
    17	        try {
    18	            System.out.println("Is your name " + args[0] +'?');     
    19	            rumpelstiltskin.guessName(args[0]); 
    20	            System.out.println("Yes! How did you guess?");
    21	            System.exit(0);
    22	        }
    23	        // come here right away if there is no args[0]
    24	        catch (IndexOutOfBoundsException e) {
    25	            System.out.println( "usage: java RumpelStiltskinDemo guess");
    26	            System.exit(0); // leave the program gracefully
    27	        }
    28	        // come here from guessName if exception thrown
    29	        catch (BadGuessException e) {
    30	            System.err.println("sorry - " + args[0] + " is not my name");
    31	        }
    32	
    33	        System.out.println(
    34	           "\nIntentionally generate a NullPointerException,\n" +
    35	           "see what the Exception's toString method returns");
    36	        try {
    37	            aNullWizard.guessName("who am I?");
    38	        }
    39	        catch (Exception e) {
    40	            System.out.println(e);
    41	        }
    42	        
    43	        System.out.println(
    44	           "\nExperiment with the printStackTrace() method:");
    45	        try {
    46	            rumpelstiltskin.makeMischief();
    47	        }
    48	        catch (Exception e) {
    49	            e.printStackTrace();
    50	        }
    51	
    52	        // perhaps throw an uncaught IndexOutOfBoundsException
    53	        System.out.println(
    54	            "\nLook for a second command line argument,\n" +
    55	            "see what happens if it's not there:" );
    56	        System.out.println(args[1]);
    57	    }
    58	
    59	    // two inner classes, used only in this file
    60	    private static class Wizard 
    61	    {
    62	        private String name;
    63	
    64	        public Wizard( String name ) 
    65	        {
    66	            this.name = name;
    67	        }
    68	
    69	        public void guessName( String name ) 
    70	            throws BadGuessException 
    71	        {
    72	            if (!name.equals(this.name))
    73	                throw new BadGuessException( );
    74	        }
    75	
    76	        public void makeMischief() 
    77	            throws BadGuessException
    78	        {
    79	            this.guessName("??");
    80	        }
    81	    }
    82	
    83	    private static class BadGuessException extends Exception  
    84	    { 
    85	        // empty body
    86	    }
    87	}