Java实现队列操作

import java.util.LinkedList;  
//单向队列  
public class Queue {  
    public Queue() {  
    }  
    private LinkedList list = new LinkedList();  
    public void put(Object v) {  
        list.addFirst(v);  
    }  
    public Object get() {  
        return list.removeLast();  
    }  
    public boolean isEmpty() {  
        return list.isEmpty();  
    }  
}
import java.util.Collection;  
import java.util.Iterator;  
import java.util.LinkedList;  
// 双向队列  
public class DQueue implements Collection {  
    private LinkedList lists;  
    public DQueue() {  
        lists = new LinkedList();  
    }  
    public void put_front(Object v) {  
        lists.addFirst(v);  
    }  
    public void put_back(Object v) {  
        lists.addLast(v);  
    }  
    public Object get_front() {  
        return lists.removeFirst();  
    }  
    public Object get_Back() {  
        return lists.removeLast();  
    }  
    public boolean isEmpty() {