用java来实现FIFO先进先出的队列

 简单实现队列先进先出:

package com;

import java.util.LinkedList;

public class MyQueue
{
    private LinkedList list = new LinkedList();

    public void put(Object t){ //加入数据
        list.addFirst(t);
    }
    public Object get(){ //取出先加入的数据
        return  list.removeLast();
    }
    public boolean isEmpt(){
       return  list.isEmpty();
    }

    public int getSize(){
        return  list.size();
    }
}

 运行:

 @Test
    public void queue () throws Exception
    {
        MyQueue myQueue = new MyQueue();
       for(int i = 0; i<10;i++){
           myQueue.put(Integer.toString(i));
       }

       while(!myQueue.isEmpt()){
           System.out.println("当前取出队列数据: "+myQueue.get());
       }
        System.out.println("当前队列数据长度: "+myQueue.getSize());
        System.out.println("当前队列数据是否为空: "+myQueue.isEmpt());
    }

结果:

 =======================================================================================

稍微复杂点的demo:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package linkedlisttest;
 
import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;
 
/**
 *
 * @author Vicky.H
 * @email [email protected]
 */
public class FIFOTest {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        FIFO fifo = new FIFOImpl(5);
        for (int i = 0; i < 20; i++) {
            A a = new A("A:" + i);
            A head = fifo.addLastSafe(a);
            System.out.println(i + "\thead:" + head + "\tsize:" + fifo.size());
        }
 
        System.out.println("---------------");
 
        System.out.println("弹出数据");
        List polls = fifo.setMaxSize(3);
        for (A a : polls) {
            System.out.println("\thead:" + a);
        }
         
        System.out.println("剩余数据");
        for (A a : fifo) {
            System.out.println("\thead:" + a);
        }
        System.out.println(fifo.size());
    }
}
 
interface FIFO extends List, Deque, Cloneable, java.io.Serializable {
 
    /**
     * 向最后添加一个新的，如果长度超过允许的最大值，则弹出一个 *
     */
    T addLastSafe(T addLast);
 
    /**
     * 弹出head，如果Size = 0返回null。而不同于pop抛出异常
     * @return 
     */
    T pollSafe();
 
    /**
     * 获得最大保存
     *
     * @return
     */
    int getMaxSize();
 
    /**
     * 设置最大存储范围
     *
     * @return 返回的是，因为改变了队列大小，导致弹出的head
     */
    List setMaxSize(int maxSize);
 
}
 
class FIFOImpl extends LinkedList implements FIFO {
 
    private int maxSize = Integer.MAX_VALUE;
    private final Object synObj = new Object();
 
    public FIFOImpl() {
        super();
    }
 
    public FIFOImpl(int maxSize) {
        super();
        this.maxSize = maxSize;
    }
 
    @Override
    public T addLastSafe(T addLast) {
        synchronized (synObj) {
            T head = null;
            while (size() >= maxSize) {
                head = poll();
            }
            addLast(addLast);
            return head;
        }
    }
 
    @Override
    public T pollSafe() {
        synchronized (synObj) {
            return poll();
        }
    }
 
    @Override
    public List setMaxSize(int maxSize) {
        List list = null;
        if (maxSize < this.maxSize) {
            list = new ArrayList();
            synchronized (synObj) {
                while (size() > maxSize) {
                    list.add(poll());
                }
            }
        }
        this.maxSize = maxSize;
        return list;
    }
 
    @Override
    public int getMaxSize() {
        return this.maxSize;
    }
}
 
class A {
 
    private String name;
 
    public A() {
    }
 
    public A(String name) {
        this.name = name;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    @Override
    public String toString() {
        return "A{" + "name=" + name + '}';
    }
}