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Java栈和队列

sqlboy-yuzhenc 人气:0

package com.yuzhenc.collection;

import java.util.Stack;

/**
 * @author: yuzhenc
 * @date: 2022-03-20 15:41:36
 * @desc: com.yuzhenc.collection
 * @version: 1.0
 */
public class Test26 {
    public static void main(String[] args) {
        Stack<String> stack = new Stack<>();
        stack.add("A");
        stack.add("B");
        stack.add("C");
        stack.add("D");
        System.out.println(stack);//[A, B, C, D]
        //判断栈是否为空
        System.out.println(stack.empty());//false
        //查看栈顶元素,不会移除
        System.out.println(stack.peek());//D
        System.out.println(stack);//[A, B, C, D]
        //查看栈顶元素,并且移除,即出栈(先进后出)
        System.out.println(stack.pop());//D
        System.out.println(stack);//[A, B, C]
        //入栈,和add方法执行的功能一样,就是返回值不同
        System.out.println(stack.push("E"));//返回入栈的元素 E
        System.out.println(stack);//[A, B, C, E]
    }
}

队列

阻塞队列

package com.yuzhenc.collection;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.TimeUnit;

/**
 * @author: yuzhenc
 * @date: 2022-03-20 16:00:22
 * @desc: com.yuzhenc.collection
 * @version: 1.0
 */
public class Test27 {
    public static void main(String[] args) throws InterruptedException {
        ArrayBlockingQueue<String> arrayBlockingQueue = new ArrayBlockingQueue<>(3);
        //添加元素
        //不可以添加null,报空指针异常
        //arrayBlockingQueue.add(null);
        //arrayBlockingQueue.offer(null);
        //arrayBlockingQueue.put(null);

        //正常添加元素
        System.out.println(arrayBlockingQueue.add("Lili"));//true
        System.out.println(arrayBlockingQueue.offer("Amy"));//true
        arrayBlockingQueue.put("Nana");//无返回值

        //队列满的情况下添加元素
        //arrayBlockingQueue.add("Sam");//报非法的状态异常
        //设置最大注阻塞时间,如果时间到了队列还是满的,就不再阻塞了
        arrayBlockingQueue.offer("Daming", 3,TimeUnit.SECONDS);
        System.out.println(arrayBlockingQueue);//[Lili, Amy, Nana]
        //真正阻塞的方法,如果队列一直是满的,就一直阻塞
        //arrayBlockingQueue.put("Lingling");//运行到这永远走不下去了,阻塞了

        //获取元素
        //获取队首元素不移除
        System.out.println(arrayBlockingQueue.peek());//Lili
        //出队,获取队首元素并且移除
        System.out.println(arrayBlockingQueue.poll());//Lili
        System.out.println(arrayBlockingQueue);//[Amy, Nana]
        //获取队首元素,并且移除
        System.out.println(arrayBlockingQueue.take());//Amy
        System.out.println(arrayBlockingQueue);//[Nana]

        //清空元素
        arrayBlockingQueue.clear();
        System.out.println(arrayBlockingQueue);//[]

        System.out.println(arrayBlockingQueue.peek());
        System.out.println(arrayBlockingQueue.poll());
        //设置阻塞事件,如果队列为空,返回null,时间到了以后就不阻塞了
        System.out.println(arrayBlockingQueue.poll(2,TimeUnit.SECONDS));
        //真正的阻塞,队列为空
        //System.out.println(arrayBlockingQueue.take());//执行到这里走不下去了
    }
}

SynchronousQueue:方便高效地进行线程间数据的传送,不会产生队列中数据争抢问题;

package com.yuzhenc.collection;

import java.util.concurrent.SynchronousQueue;

/**
 * @author: yuzhenc
 * @date: 2022-03-20 21:06:47
 * @desc: com.yuzhenc.collection
 * @version: 1.0
 */
public class Test28 {
    public static void main(String[] args) {
        SynchronousQueue sq = new SynchronousQueue();
        //创建一个线程,取数据:
        new Thread(new Runnable() {
            @Override
            public void run() {
                while(true){
                    try {
                        System.out.println(sq.take());
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
        //搞一个线程,往里面放数据:
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    sq.put("aaa");
                    sq.put("bbb");
                    sq.put("ccc");
                    sq.put("ddd");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}
package com.yuzhenc.collection;

import java.util.concurrent.PriorityBlockingQueue;

/**
 * @author: yuzhenc
 * @date: 2022-03-20 21:16:56
 * @desc: com.yuzhenc.collection
 * @version: 1.0
 */
public class Test29 {
    public static void main(String[] args) throws InterruptedException {
        PriorityBlockingQueue<Human> priorityBlockingQueue = new PriorityBlockingQueue<>();
        priorityBlockingQueue.put(new Human("Lili",25));
        priorityBlockingQueue.put(new Human("Nana",18));
        priorityBlockingQueue.put(new Human("Amy",38));
        priorityBlockingQueue.put(new Human("Sum",9));
        //没有按优先级排列
        System.out.println(priorityBlockingQueue);//[Human{name='Sum', age=9}, Human{name='Nana', age=18}, Human{name='Amy', age=38}, Human{name='Lili', age=25}]
        //出列的时候按优先级出列
        System.out.println(priorityBlockingQueue.take());//Human{name='Sum', age=9}
        System.out.println(priorityBlockingQueue.take());//Human{name='Nana', age=18}
        System.out.println(priorityBlockingQueue.take());//Human{name='Lili', age=25}
        System.out.println(priorityBlockingQueue.take());//Human{name='Amy', age=38}
    }
}

class Human implements Comparable <Human> {
    String name;
    int age;

    public Human() {}

    public Human(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Human{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    @Override
    public int compareTo(Human o) {
        return this.age-o.age;
    }
package com.yuzhenc.collection;

import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;

/**
 * @author: yuzhenc
 * @date: 2022-03-20 21:43:32
 * @desc: com.yuzhenc.collection
 * @version: 1.0
 */
public class Test30 {
    //创建一个队列:
    DelayQueue<User> dq = new DelayQueue<>();
    //登录游戏:
    public void login(User user){
        dq.add(user);
        System.out.println("用户:[" + user.getId() +"],[" + user.getName() + "]已经登录,预计下机时间为:" + user.getEndTime() );
    }
    //时间到,退出游戏,队列中移除:
    public void logout(){
        //打印队列中剩余的人:
        System.out.println(dq);
        try {
            User user = dq.take();
            System.out.println("用户:[" + user.getId() +"],[" + user.getName() + "]上机时间到,自动退出游戏");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    //获取在线人数:
    public int onlineSize(){
        return dq.size();
    }
    //这是main方法,程序的入口
    public static void main(String[] args) {
        //创建测试类对象:
        Test30 test = new Test30();
        //添加登录的用户:
        test.login(new User(1,"张三",System.currentTimeMillis()+5000));
        test.login(new User(2,"李四",System.currentTimeMillis()+2000));
        test.login(new User(3,"王五",System.currentTimeMillis()+10000));
        //一直监控
        while(true){
            //到期的话,就自动下线:
            test.logout();
            //队列中元素都被移除了的话,那么停止监控,停止程序即可
            if(test.onlineSize() == 0){
                break;
            }
        }
    }
}
class User implements Delayed {
    private int id;//用户id
    private String name;//用户名字
    private long endTime;//结束时间
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public long getEndTime() {
        return endTime;
    }
    public void setEndTime(long endTime) {
        this.endTime = endTime;
    }
    public User(int id, String name, long endTime) {
        this.id = id;
        this.name = name;
        this.endTime = endTime;
    }
    //只包装用户名字就可以
    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                '}';
    }
    @Override
    public long getDelay(TimeUnit unit) {
        //计算剩余时间 剩余时间小于0 <=0  证明已经到期
        return this.getEndTime() - System.currentTimeMillis();
    }
    @Override
    public int compareTo(Delayed o) {
        //队列中数据 到期时间的比较
        User other = (User)o;
        return ((Long)(this.getEndTime())).compareTo((Long)(other.getEndTime()));
    }
}

在这里插入图片描述

双端队列

package com.yuzhenc.collection;

import java.util.Deque;
import java.util.LinkedList;

/**
 * @author: yuzhenc
 * @date: 2022-03-20 22:03:36
 * @desc: com.yuzhenc.collection
 * @version: 1.0
 */
public class Test31 {
    public static void main(String[] args) {
        /*
        双端队列:
        Deque<E> extends Queue
        Queue一端放 一端取的基本方法  Deque是具备的
        在此基础上 又扩展了 一些 头尾操作(添加,删除,获取)的方法
         */
        Deque<String> d = new LinkedList<>() ;
        d.offer("A");
        d.offer("B");
        d.offer("C");
        System.out.println(d);//[A, B, C]
        d.offerFirst("D");
        d.offerLast("E");
        System.out.println(d);//[D, A, B, C, E]
        System.out.println(d.poll());//D
        System.out.println(d);//[A, B, C, E]
        System.out.println(d.pollFirst());//A
        System.out.println(d.pollLast());//E
        System.out.println(d);//[B, C]
    }
}

总结

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