线程的操作

线程操作

线程停止

package com.state;
 
//测试stop
//1、建议线程正常停止-->利用次数，不建议死循环
//2、建议使用标志为-->设置一个标志位
//3、不要使用stop或者destroy等过时的方法
public class StateTest01 implements Runnable {
 
    //1、设置一个标志位
    private boolean flag = true;
 
    @Override
    public void run() {
        int i = 0;
        while (flag) {
            System.out.println("run...Thread " + i++);
        }
 
    }
 
    //2、设置一个公开的方法停止线程，转换标志为
    public void stop() {
        this.flag = false;
    }
 
    public static void main(String[] args) {
        StateTest01 stateTest01 = new StateTest01();
        new Thread(stateTest01).start();
 
 
        for (int i = 0; i < 1000; i++) {
            System.out.println("main " + i);
            if (i == 900) {
                //调用stop方法切换标志位，停止线程
                stateTest01.stop();
                System.out.println("线程该停止了");
            }
        }
    }
 
}

image

线程休眠

模拟网络延时

package com.state;
 
 
//模拟网络延时:放大问题的发生性
public class SleepTest01 implements Runnable {
 
    private int ticketNum = 10;
 
 
    @Override
    public void run() {
        while (true) {
            if (ticketNum <= 0) {
                break;
            }
 
            //模拟延时
            try {
                Thread.sleep(800);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "-->拿到了第 " + ticketNum-- + " 张票");
        }
    }
 
    public static void main(String[] args) {
        SleepTest01 sleepTest01 = new SleepTest01();
 
        new Thread(sleepTest01, "小明").start();
        new Thread(sleepTest01, "老师").start();
        new Thread(sleepTest01, "黄牛").start();
    }
}

模拟倒计时

package com.state;
 
//模拟倒计时
public class SleepTest02 {
 
    public static void main(String[] args) {
        try {
            tenDown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
 
 
    public static void tenDown() throws InterruptedException {
        int num = 10;
        while (true) {
            Thread.sleep(1000);
            System.out.println(num--);
            if (num <= 0) break;
        }
    }
}

打印当前系统时间

package com.state;
 
import java.text.SimpleDateFormat;
import java.util.Date;
 
//打印当前系统时间
//每个对象都有一把锁，sleep不会释放锁
public class SleepTest03 {
    public static void main(String[] args) {
        Date startTime = new Date(System.currentTimeMillis());//获取当前系统时间
 
        while (true) {
            try {
                Thread.sleep(1000);
                System.out.println(new SimpleDateFormat("HH:mm:ss").format(startTime));
                startTime = new Date(System.currentTimeMillis());//变更当前时间
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
 
 
    }
 
 
    public static void tenDown() throws InterruptedException {
        int num = 10;
        while (true) {
            Thread.sleep(1000);
            System.out.println(num--);
            if (num <= 0) break;
        }
    }
}

线程礼让

代码：

package com.state;
 
//测试礼让线程
//礼让不一定能成功，需要看CPU的调度
public class YieldTest01 {
 
    public static void main(String[] args) {
        MyYield myYield = new MyYield();
 
        new Thread(myYield,"a").start();
        new Thread(myYield,"b").start();
    }
    
}
 
class MyYield implements Runnable {
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + "线程开始执行");
        Thread.yield();
        System.out.println(Thread.currentThread().getName() + "线程停止执行");
    }
}

礼让成功：

image

image

线程强制执行_join

join合并线程，待此线程执行完成后，再执行其他线程，其他线程阻塞

package com.state;
 
 
//测试join方法
public class JoinTest01 implements Runnable {
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println("插队线程来了：" + i);
        }
    }
 
    public static void main(String[] args) throws InterruptedException {
 
 
        //启动我们的线程
        JoinTest01 joinTest01 = new JoinTest01();
        Thread thread = new Thread(joinTest01);
        thread.start();
 
 
        //主线程
        for (int i = 0; i < 500; i++) {
            if (i == 200) {
                thread.join();//插队
            }
            System.out.println("main:" + i);
        }
 
    }
}

线程状态

package com.state;
 
//观察测试线程的状态
public class StateTest02 {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println(".....");
        });
 
 
        //观察状态
        Thread.State state = thread.getState();
        System.out.println(state);
 
        //观察启动后
        thread.start();//启动线程
        state=thread.getState();
        System.out.println(state);//Run
 
        while (state!= Thread.State.TERMINATED){
            Thread.sleep(100);
            state=thread.getState();
            System.out.println(state);
        }
 
    }
}

线程一旦死亡，就不能再次启动

线程的优先级

  • Java提供一个线程调度器来监控程序中启动后进入就绪状态的所有线程，线程调度器按照优先级决定应该调度哪个线程

  • 线程的优先级用数字、表示，范围从1~10

    • Thread.MIN_PRIORITY = 1;
    • Thread.MAX_PRIORITY = 10;
    • Thread.NORM_PRIORITY = 5;

  • 使用以下方式改变或获取优先级

    • getPriority().setPriority(int xxx)
package com.state;
 
public class PriorityTest01 {
 
    public static void main(String[] args) {
 
        // 主线程默认优先级
        System.out.println(Thread.currentThread().getName() + "-->" + Thread.currentThread().getPriority());
 
        MyPriority myPriority = new MyPriority();
 
        Thread t1 = new Thread(myPriority);
        Thread t2 = new Thread(myPriority);
        Thread t3 = new Thread(myPriority);
        Thread t4 = new Thread(myPriority);
        Thread t5 = new Thread(myPriority);
        Thread t6 = new Thread(myPriority);
 
        //先设置优先级，在再启动
        t1.start();
 
        t2.setPriority(1);
        t2.start();
 
        t3.setPriority(3);
        t3.start();
 
        t4.setPriority(Thread.MAX_PRIORITY);//10
        t4.start();
 
        t5.setPriority(6);
        t5.start();
 
        t6.setPriority(8);
        t6.start();
 
    }
 
}
 
class MyPriority implements Runnable {
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + "-->" + Thread.currentThread().getPriority());
    }
}

优先级低并不意味着获得调度的概率低，并不是优先级低就不会被调用了，具体需要看CPU调度

守护线程（daemon）

  • 线程分为守护线程和用户线程
  • 虚拟机必须确保用户线程执行完毕
  • 虚拟机不用等待守护线程执行完毕
  • 守护线程如：后台记录操作日志，监控内存，垃圾回收等待
package com.state;
 
public class DaemonTest01 {
 
    public static void main(String[] args) {
 
        god god = new god();
        You you = new You();
 
        Thread thread = new Thread(god);
        thread.setDaemon(true);//默认值false表示是用户线程，正常的线程都是用户线程
 
        thread.start();//上帝守护线程启动
 
        new Thread(you).start();//用户线程启动--你
 
    }
 
}
 
 
//上帝
class god implements Runnable {
    @Override
    public void run() {
        while (true) {
            System.out.println("上帝保佑着你！！");
        }
    }
}
 
 
//你
class You implements Runnable {
 
    @Override
    public void run() {
        for (int i = 0; i < 36500; i++) {
            System.out.println("你开心的活着");
        }
        System.out.println("====goodbye, the world!!!====");
    }
}

image

线程同步机制

并发：多个线程访问同一个对象

线程不安全

1、

package com.syn;
 
//不安全的买票
public class UnsafeBuyTicket {
 
    public static void main(String[] args) {
        BuyTicket buyTicket = new BuyTicket();
 
        new Thread(buyTicket, "小明").start();
        new Thread(buyTicket, "小红").start();
        new Thread(buyTicket, "黄牛").start();
 
    }
 
}
 
 
class BuyTicket implements Runnable {
 
    private int ticketNums = 10;
    boolean flag = true;//外部停止方式
 
    @Override
    public void run() {
        //买票
        while (flag) {
            try {
                buy();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
 
    private void buy() throws InterruptedException {
        //判断是否有票
        if (ticketNums <= 0) {
            return;
        }
        //模拟延时
        Thread.sleep(100);
        //买票
        System.out.println(Thread.currentThread().getName() + "拿到了" + ticketNums--);
    }
}

运行结果：
image

2、

package com.syn;
 
//不安全的取钱
public class UnsafeBank {
 
    public static void main(String[] args) {
        Account account = new Account(100, "结婚基金");
 
        Drawing you = new Drawing(account, 50, "你");
        Drawing girl = new Drawing(account, 100, "girl");
 
        you.start();
        girl.start();
    }
 
}
 
 
//账户
class Account {
    int money;
    String name;
 
    public Account(int money, String name) {
        this.money = money;
        this.name = name;
    }
 
}
 
 
//银行
class Drawing extends Thread {
 
    //账户
    Account account;
 
    //取钱金额
    int drawingMoney;
 
    //现在手里有多少钱
    int nowMoney;
 
    public Drawing(Account account, int drawingMoney, String name) {
        super(name);
        this.account = account;
        this.drawingMoney = drawingMoney;
    }
 
    //取钱
    @Override
    public void run() {
        //判断有没有钱
        if (account.money - drawingMoney < 0) {
            System.out.println(Thread.currentThread().getName() + "账户余额不足，无法取现！");
            return；
        }
 
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
 
        //卡上余额更新
        account.money = account.money - drawingMoney;
 
        //手上现金更新
        nowMoney = nowMoney + drawingMoney;
 
        //输出
        System.out.println("卡上余额为：" + account.money);
        //Thread.currentThread().getName() = this.getName()
        System.out.println(this.getName() + "手上的现金为：" + nowMoney);
    }
}

运行结果：

image

3、

package com.syn;
 
import java.util.ArrayList;
import java.util.List;
 
//线程不安全的集合
public class UnsafeList {
 
    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
 
        for (int i = 0; i < 10000; i++) {
            new Thread(() -> {
                list.add(Thread.currentThread().getName());
            }).start();
        }
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}

运行结果：
image

同步方法

synchronized同步方法

1、安全买票

package com.syn;
 
//不安全的买票
public class UnsafeBuyTicket {
 
    public static void main(String[] args) {
        BuyTicket buyTicket = new BuyTicket();
 
        new Thread(buyTicket, "小明").start();
        new Thread(buyTicket, "小红").start();
        new Thread(buyTicket, "黄牛").start();
 
    }
 
}
 
 
class BuyTicket implements Runnable {
 
    private int ticketNums = 10;
    boolean flag = true;//外部停止方式
 
    @Override
    public void run() {
        //买票
        while (flag) {
            try {
                buy();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
 
    //synchronized同步方法，锁的是this
    private synchronized void buy() throws InterruptedException {
        //判断是否有票
        if (ticketNums <= 0) {
            return;
        }
        //模拟延时
        Thread.sleep(100);
        //买票
        System.out.println(Thread.currentThread().getName() + "拿到了" + ticketNums--);
    }
}

运行结果：
image

2、安全取钱

package com.syn;
 
//不安全的取钱
public class UnsafeBank {
 
    public static void main(String[] args) {
        Account account = new Account(100, "结婚基金");
 
        Drawing you = new Drawing(account, 50, "你");
        Drawing girl = new Drawing(account, 100, "girl");
 
        you.start();
        girl.start();
    }
 
}
 
 
//账户
class Account {
    int money;
    String name;
 
    public Account(int money, String name) {
        this.money = money;
        this.name = name;
    }
 
}
 
 
//银行
class Drawing extends Thread {
 
    //账户
    Account account;
 
    //取钱金额
    int drawingMoney;
 
    //现在手里有多少钱
    int nowMoney;
 
    public Drawing(Account account, int drawingMoney, String name) {
        super(name);
        this.account = account;
        this.drawingMoney = drawingMoney;
    }
 
    //取钱
    //synchronized默认锁的是this本身
    @Override
    public void run() {
 
        //锁的对象是变化的量,需要增删改的对象
        synchronized (account) {
            //判断有没有钱
            if (account.money - drawingMoney < 0) {
                System.out.println(Thread.currentThread().getName() + "账户余额不足，无法取现！");
                return;
            }
 
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
 
            //卡上余额更新
            account.money = account.money - drawingMoney;
 
            //手上现金更新
            nowMoney = nowMoney + drawingMoney;
 
            //输出
            //Thread.currentThread().getName() = this.getName()
            System.out.println(this.getName() + "手上取得的现金为：" + nowMoney);
            System.out.println("卡上余额为：" + account.money);
        }
    }
 
 
}

运行结果：
image

3、锁集合的线程

package com.syn;
 
import java.util.ArrayList;
import java.util.List;
 
//线程不安全的集合
public class UnsafeList {
 
    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
 
        for (int i = 0; i < 10000; i++) {
            new Thread(() -> {
                synchronized (list) {
                    list.add(Thread.currentThread().getName());
                }
 
            }).start();
        }
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}

运行结果

image

CopyOnWriteArrayList

一种线程安全的集合

package com.syn;
 
 
import java.util.concurrent.CopyOnWriteArrayList;
 
//测试JUC安全类型的集合
public class TestJUC {
 
    public static void main(String[] args) {
        CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<String>();
        for (int i = 0; i < 10000; i++) {
            new Thread(
                    () -> {
                        list.add(Thread.currentThread().getName());
                    }
            ).start();
        }
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}

死锁

两个或者多个线程都在等待对方释放资源，都停止执行的情形；

某一个同步块同时拥有“两个以上对象的锁”时，就可能会发生死锁的问题。

死锁代码：

package com.thread;
 
public class DeadLock {
    public static void main(String[] args) {
        Makeup girl1 = new Makeup(0, "灰姑凉");
        Makeup girl2 = new Makeup(1, "白雪公主");
 
        girl1.start();
        girl2.start();
 
    }
}
 
//口红
class LipStick {
 
}
 
 
//镜子
class Mirror {
 
}
 
 
class Makeup extends Thread {
 
    //需要的资源自由一份，用static来修饰
    static LipStick lipStick = new LipStick();
    static Mirror mirror = new Mirror();
 
    int choice;//选择
    String name;//化妆的人
 
    public Makeup(int choice, String name) {
        this.choice = choice;
        this.name = name;
    }
 
 
    @Override
    public void run() {
        //化妆
        try {
            makeup();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
 
    //化妆，互相持有对方的锁，就是需要拿到对方的资源
    private void makeup() throws InterruptedException {
 
        if (choice == 0) {
            synchronized (lipStick) {//获得口红的锁
                System.out.println(this.name + "获得口红的锁");
                Thread.sleep(1000);
 
                synchronized (mirror) {//一秒钟后获得镜子的锁
                    System.out.println(this.name + "获得镜子的锁");
                }
 
            }
        } else {
            synchronized (mirror) {//获得镜子的锁
                System.out.println(this.name + "获得镜子的锁");
                Thread.sleep(2000);
 
                synchronized (lipStick) {//一秒钟后获得口红的锁
                    System.out.println(this.name + "获得口红的锁");
                }
 
            }
 
        }
    }
}

image

可以看见两个对象的锁都卡住了

优化代码:

package com.thread;
 
public class DeadLock {
    public static void main(String[] args) {
        Makeup girl1 = new Makeup(0, "灰姑凉");
        Makeup girl2 = new Makeup(1, "白雪公主");
 
        girl1.start();
        girl2.start();
 
    }
}
 
//口红
class LipStick {
 
}
 
 
//镜子
class Mirror {
 
}
 
 
class Makeup extends Thread {
 
    //需要的资源自由一份，用static来修饰
    static LipStick lipStick = new LipStick();
    static Mirror mirror = new Mirror();
 
    int choice;//选择
    String name;//化妆的人
 
    public Makeup(int choice, String name) {
        this.choice = choice;
        this.name = name;
    }
 
 
    @Override
    public void run() {
        //化妆
        try {
            makeup();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
 
    //化妆，互相持有对方的锁，就是需要拿到对方的资源
    private void makeup() throws InterruptedException {
 
        if (choice == 0) {
            synchronized (lipStick) {//获得口红的锁
                System.out.println(this.name + "获得口红的锁");
                Thread.sleep(1000);
            }
            synchronized (mirror) {//一秒钟后获得镜子的锁
                System.out.println(this.name + "获得镜子的锁");
            }
        } else {
            synchronized (mirror) {//获得镜子的锁
                System.out.println(this.name + "获得镜子的锁");
                Thread.sleep(2000);
            }
            synchronized (lipStick) {//一秒钟后获得口红的锁
                System.out.println(this.name + "获得口红的锁");
            }
 
        }
    }
}

image

将包含的锁拿出来，用完了后释放

Lock锁

  • ReentrantLock锁是可重读锁

  • Lock是显式锁（手动开启和关闭锁），synchronized是隐式锁，出了作用域自动释放

  • Lock只有代码块锁，synchronized有代码块锁和方法锁

  • 使用Lock锁，JVM将花费较少的时间来调度线程，性能更好。并且具有更好的扩展性

  • 优先使用顺序：

    • Lock > 同步代码块 > 同步方法

实现代码：

package com.syn;
 
import sun.util.resources.cldr.chr.TimeZoneNames_chr;
 
import java.security.PrivateKey;
import java.util.concurrent.locks.ReentrantLock;
 
public class LockTest01 {
    public static void main(String[] args) {
        LockTest02 lockTest02 = new LockTest02();
 
        new Thread(lockTest02).start();
        new Thread(lockTest02).start();
        new Thread(lockTest02).start();
    }
 
}
 
 
class LockTest02 implements Runnable {
    int ticketNums = 10;
 
    //定义Lock锁
    private final ReentrantLock lock = new ReentrantLock();
 
    @Override
    public void run() {
        while (true) {
            try {//加锁
                lock.lock();
                if (ticketNums > 0) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(ticketNums--);
                } else {
                    break;
                }
            } finally {
                //解锁
                lock.unlock();
            }
        }
    }
}

运行结果：
image

posted @   每年桃花开的时候  阅读(25)  评论(0)  编辑  收藏  举报
相关博文：
·  Scanner的使用
·  Java循环结构
·  线程状态03
·  JAVA多线程
·  Thread多线程基础02
阅读排行：
· 分享一个免费、快速、无限量使用的满血 DeepSeek R1 模型，支持深度思考和联网搜索！
· 使用C#创建一个MCP客户端
· 基于 Docker 搭建 FRP 内网穿透开源项目（很简单哒）
· ollama系列1：轻松3步本地部署deepseek，普通电脑可用
· 按钮权限的设计及实现
点击右上角即可分享
微信分享提示
AI IDE Trae