/*
  Author  : Michael Robinson
  Program : queue.java  
  Purpose : Queue is a data structure that allows us to place
            data items one after another.

            It uses the FIFO (First In, First Out) processing method. 
            The first item placed in the queue is the first
            item to be extracted/processed.
              
            To create an object of the Queue class we use:
               Queue<String> queue = new LinkedList<String>();
            
            To place items in the queue we use the command
               queue.add( "FirstQ" );
            
            To extract items in the queue we use the command
               queue.poll();
             
               if we are using an iterator such as:
                  Iterator itq = queue.iterator();
                
               we first need to check if the queue has more items:
                  itq.hasNext()
                
               then we remove the data using:
               itqProcess.remove();
                
               we can see the first item in the queue using:
               queue.peek();
             
            For more details see :
                
        http://docs.oracle.com/javase/6/docs/api/java/util/Queue.html
               
            There is another type of queue called priority queue.
          
  Updated : October 26, 2099
*/
 
 
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;


public class queue 
{
    public static void printTheQueue(
                       Queue<String> queue, String message )
    {
        System.out.printf( "  Adding...  %d = Size of Queue : %s\n",  
                              queue.size(), queue );

    }


    public static void reqularQueue()
    {
        String message = "Adding items is the queue,";

        Queue<String> queue = new LinkedList<String>();
           
        System.out.printf( "We now start with an empty queue :" +   
                           " %s\n\n", queue );
            
        queue.add( "FirstQ" );
        printTheQueue( queue, message );
             
        queue.add( "SecondQ" );
        printTheQueue( queue, message );
         
        queue.add( "ThirdQ" );
        printTheQueue( queue, message );
             
        queue.add( "FourQ" );
        printTheQueue( queue, message );
          
        System.out.println("\nFIFO order means, First In First Out");
        
        System.out.println( "\nLet's see the top of the Queue in" +
                            " FIFO order : " + queue.peek() );
        Iterator itq = queue.iterator();

        System.out.printf( "\nLet's see what is in the Queue in " +
                           "FIFO order: %s\n", queue );
            
        System.out.printf("\n  Let's see again \t .. left in queue");
        
        while( itq.hasNext() ) //start at the top of the queue
        { 
            System.out.printf( " %s ", ( String )itq.next() );
        }
         
        System.out.printf( "\n  processing  %s", queue.peek() ); 
        queue.poll();
        System.out.printf( "\t .. left in queue %s \n", queue );
           
        Iterator itqProcess = queue.iterator();
        
        //start at the top of the queue
        while( itqProcess.hasNext() ) 
        { 
            System.out.printf( "  processing  %s ", ( String )
                                   itqProcess.next() );
             
            itqProcess.remove();
            System.out.printf("\t .. left in queue %s \n", queue );
        }
             
        System.out.println( "\nFinal Size of Queue : " +
                             queue.size() );
               
        System.out.printf( "We end with an empty queue : %s\n\n", 
                            queue );
         
    }//end  public static void reqularQueue()
     
          
    public static void main(String[] args) 
    {
       reqularQueue();
       
    }//end public static void main(String[] args) 
    
}//end public class queue