BELOW YOU WILL FIND THE CODE FOR THE 
Queue Interface and a class that implements that Interface
- Copy the Interface code into a new Interface
- Copy the Class code into a new Class

//=============================================================
/**
 * Interface for a Queue
 * 
 * @author Appears in Litvin's "Be Prepared"
 */

public interface Queue
{
    boolean isEmpty();
    void enqueue(Object x);
    Object dequeue();
    Object peekFront(); // returns the first item without removing it
}

//===============================================

import java.util.LinkedList;

/**
 * This class implements the Queue interface using a linked list.
 * 
 * @author Appears in Litvin's "Be Prepared"
 */

public class ListQueue implements Queue
{
    private LinkedList items;
        
    // Constructor initializes a new linked list     
    public ListQueue() { items = new LinkedList(); }    
    public boolean isEmpty() { return items.size() == 0;}
    public void enqueue(Object obj) { items.addLast(obj); }
    public Object dequeue() { return items.removeFirst(); }
    public Object peekFront() { return items.getFirst(); }    
}