Main.java

package ca.ubc.cs.spl.aspectPatterns.examples.state.java;

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 * Version 1.1 (the "License"); you may not use this file except in
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 *
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 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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 *
 * The Original Code is ca.ubc.cs.spl.aspectPatterns.
 * 
 * For more details and the latest version of this code, please see:
 * http://www.cs.ubc.ca/labs/spl/projects/aodps.html
 *
 * Contributor(s):   
 */

/**
 * Implements the driver for the State design pattern example.<p> 
 *
 * Intent: <i>Allow an object to alter its behavior when its internal state
 * changes. The object will appear to change its class</i><p>
 *
 * Participating objects are <code>Queue</code> as <i>Context</i>, and 
 * <code>QueueNormal</code>, <code>QueueEmpty</code>, and <code>QueueFull
 * </code> as <i>ConcreteState</i>s. The <i>State</i> interface is defined in
 * <code>QueueState</code>. This version implements an update-on-demand
 * logic (see GoF, implementation 1, page 308). The logic requires passing
 * the context to calls to methods defined on the state interface, and an
 * interface for context objects. The interface is defined in 
 * <code>QueueContext</code>.
 * <p> 
 *
 * This example of the State design pattern models a Queue ADT with
 * a limited capacity that has three different states: 
 * <UL>
 * <LI>Empty:	The queue is empty 
 * <LI>Normal:  The queue is neither empty nor full
 * <LI>Full:	The queue is full (# of elements = capacity)
 * </UL>
 * The queue stores Objects. The following operations are defined on Queue:
 * <UL>
 * <LI><code>insert(Object)</code> Inserts a new Object into the queue
 * <LI><code>getFirst():Object</code> Returns the first element in the queue
 * <LI><code>removeFirst()</code> Removes the first elelemts from the queue
 * </UL>
 * These are the pattern roles:
 * <UL>
 * <LI>Queue:	Context
 * <LI>QueueState: 	State interface
 * <LI>QueueEmpty:  ConcreteState1
 * <LI>QueueNormal: ConcreteState2
 * <LI>QueueFull:	ConcreteState3 
 * </UL>
 * This implementation passes the context as an argument to its method 
 * calls to state objects, thus allowing for update on demand and removing
 * the constraint that Queue has to ask the states for the successor state
 * after each call.
 *
 * According to GoF, this implementation is generally more flexible than 
 * having the state transitions fixed in the context object. Note however
 * that this approach results in a tight coupling of <i>ConcreteState</i>s
 * and <i>Context</i> objects.
 *
 * <p><i>This is the Java version.</i><p>
 *
 * @author  Jan Hannemann
 * @author  Gregor Kiczales
 * @version 1.1, 02/17/04
 * 
 * @see QueueContext
 * @see Queue
 * @see QueueState
 * @see QueueEmpty
 * @see QueueNormal
 * @see QueueFull
 */


public class Main { 
    
    /**
     * Implements insertion into a queue. Prints out status messages.
     *
     * @param queue the queue to insert into
     * @param s the string to insert into the queue
     */     	

	private static void testInsert(Queue queue, String s) {
		System.out.print("   Trying to insert ["+s+"] into the queue ... ");
		boolean status = queue.insert(s);
		if (status == true) {
			System.out.println("successful"); 
		} else {
			System.out.println("NOT successful, queue probably full");
		}
	}

    /**
     * Implements deletion from a queue. Prints out status messages.
     *
     * @param queue the queue to delete items from
     */     	

	private static void testRemove(Queue queue) {
		System.out.print("   Trying to remove 1st element of the queue ... ");
		String item = (String) queue.getFirst(); 
		boolean status = queue.removeFirst();
		if (status == true) {
			System.out.println("successful: "+item); 
		} else {
			System.out.println("NOT successful: "+item);
		}
	}

    /**
     * Implements the driver for the State design pattern example.<p> 
     *
     * @param args the command line paramters, unused
     */

	public static void main(String[] args) {

		System.out.println("Testing Pattern: State - STARTING\n");
		
		Queue queue = new Queue();
		testInsert(queue, "This ");
		testInsert(queue, "is ");  
		testInsert(queue, "a ");
		testInsert(queue, "test");   
		System.out.println();
		testRemove(queue);
		testRemove(queue);
		testRemove(queue);
		testRemove(queue);

		System.out.println("\nTesting Pattern: State - FINISHED");
	}
}