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Java多线程进阶

news 2025/7/20 17:54:08

目录​​​​​​​

一、线程状态

1.线程五大状态

  运行过程描述

2.线程方法

2.1停止线程

2.2线程休眠

2.3线程礼让

2.4线程插队

3.线程状态观测

4.线程优先级

5.守护(daemon)线程

二、线程同步

1.介绍

2.不安全的线程案例

3.同步方法

4.同步块

5.死锁

死锁避免办法

6.Lock(锁)

7.synchroized与Lock对比

五、线程通信问题

1.线程通信方法

2.线程通信问题解决方式

六、线程池

一、线程状态

1.线程五大状态

  1. 新建状态
  2. 就绪状态
  3. 运行状态
  4. 阻塞状态
  5. 死亡状态

  运行过程描述

      

2.线程方法

2.1停止线程

案例：

public class ThreadStop implements Runnable {private Boolean flag = true;@Overridepublic void run() {int count = 0;while (flag) {System.out.println("线程正在运行" + count++);}}public void stop() {this.flag = false;}public static void main(String[] args) {ThreadStop stop = new ThreadStop();new Thread(stop).start();for (int i = 0; i < 1000; i++) {System.out.println("主函数正在运行" + i);if (i == 900) {stop.stop();}}}
}
2.2线程休眠

案例：

public class ThreadSleep {public static void sleepThread() {int num = 10;while (true) {try {System.out.println("倒计时:" + num--);Thread.sleep(1000);if (num <= 0) {break;}} catch (InterruptedException e) {throw new RuntimeException(e);}}}public static void main(String[] args) {sleepThread();}
}
2.3线程礼让

        线程礼让只是重新抢夺CPU的调度，礼让不一定会成功、只是再给其它线程一个机会而已。

案例：

public class ThreadYield implements Runnable {@Overridepublic void run() {System.out.println(Thread.currentThread().getName() + "开始运行");Thread.yield();System.out.println(Thread.currentThread().getName() + "结束运行");}public static void main(String[] args) {new Thread(new ThreadYield(), "线程1").start();new Thread(new ThreadYield(), "线程2").start();}
}
2.4线程插队

        简单的理解为线程插队就可以了

案例：

public class ThreadJoin implements Runnable {@Overridepublic void run() {for (int i = 1; i <= 1000; i++) {System.out.println("我是VIP我要插队" + i);}}public static void main(String[] args) throws InterruptedException {ThreadJoin threadJoin = new ThreadJoin();Thread thread = new Thread(threadJoin);thread.start();for (int i = 1; i <= 100; i++) {System.out.println("我是普通用户:" + i);if (i == 50) {thread.join();}}}
}

3.线程状态观测

案例：

public class GetThreadState implements Runnable {// 实现Runnable接口，重写run方法@Overridepublic void run() {// 循环一次for (int i = 0; i < 1; i++) {try {// 休眠500毫秒Thread.sleep(500);} catch (InterruptedException e) {// 抛出运行时异常throw new RuntimeException(e);}}}public static void main(String[] args) {// 创建GetThreadState对象Thread thread = new Thread(new GetThreadState());// 输出线程状态System.out.println(thread.getState());thread.start();System.out.println(thread.getState());while (thread.getState()!= Thread.State.TERMINATED){System.out.println(thread.getState());}System.out.println(thread.getState());}
}

4.线程优先级

        线程优先级的高低只是被CPU调用的概率大

案例:

public class ThreadPriority implements Runnable {@Overridepublic void run() {synchronized (ThreadPriority.class){System.out.println(Thread.currentThread().getName() + "--->" + Thread.currentThread().getPriority());}}public static void main(String[] args) {Thread one = new Thread(new ThreadPriority(), "one");one.setPriority(1);one.start();Thread two = new Thread(new ThreadPriority(), "two");two.setPriority(2);two.start();Thread three = new Thread(new ThreadPriority(), "three");three.setPriority(3);three.start();Thread four = new Thread(new ThreadPriority(), "four");four.setPriority(4);four.start();Thread five = new Thread(new ThreadPriority(), "five");five.setPriority(5);five.start();Thread defaultPriority = new Thread(new ThreadPriority(), "defaultPriority");defaultPriority.start();Thread maxPriority = new Thread(new ThreadPriority(), "maxPriority");maxPriority.setPriority(Thread.MAX_PRIORITY);maxPriority.start();}
}

5.守护(daemon)线程

        皇上和宫女，皇上活着宫女一直在，皇上死了宫女陪葬

案例：

package com.example.threadstudy.state;public class DaemonThread {public static void main(String[] args) {// 创建一个God对象God god = new God();// 创建一个Person对象Person person = new Person();// 创建一个Thread对象，并将God对象作为参数传入Thread thread = new Thread(god);// 将Thread对象设置为守护线程thread.setDaemon(true);// 启动Thread对象thread.start();// 创建一个新的Thread对象，并将Person对象作为参数传入new Thread(person, "one").start();new Thread(person, "two").start();}}class God implements Runnable {// 实现Runnable接口，重写run方法@Overridepublic void run() {// 无限循环while (true)// 输出上帝一直保佑你System.out.println("上帝一直保佑你");}
}class Person implements Runnable {// 实现Runnable接口，重写run方法@Overridepublic void run() {// 循环100次for (int i = 0; i < 100; i++) {// 输出"我还在坚持"System.out.println(Thread.currentThread().getName() + "我还在坚持");}// 输出"坚持不住了,上帝再见"System.out.println(Thread.currentThread().getName() + "坚持不住了,上帝再见");}
}

二、线程同步

1.介绍

        多个线程操作同一个资源

2.不安全的线程案例

package com.example.threadstudy.unsafethread;public class BuyTicket implements Runnable {private int ticket = 10;@Overridepublic void run() {while (true) {if (hasTicket()) {try {Thread.sleep(50);System.out.println(Thread.currentThread().getName() + "买到了第" + ticket-- + "张票");} catch (InterruptedException e) {throw new RuntimeException(e);}} else {break;}}System.out.println("票已经卖完了");}public Boolean hasTicket() {return ticket > 0;}public static void main(String[] args) {new Thread(new BuyTicket(), "窗口1").start();new Thread(new BuyTicket(), "窗口2").start();new Thread(new BuyTicket(), "窗口3").start();}
}

3.同步方法

        同步方法,锁的是当前对象，未添加synchronized的方法也会被锁上，浪费资源
实现:
public class BuyTicket {public static void main(String[] args) {BuyTicketThread buyTicketThread = new BuyTicketThread();Thread thread1 = new Thread(buyTicketThread, "窗口1");Thread thread2 = new Thread(buyTicketThread, "窗口2");Thread thread3 = new Thread(buyTicketThread, "窗口3");thread1.start();thread2.start();thread3.start();}
}
class BuyTicketThread implements Runnable {private int ticket = 10;private boolean hasTicketFlag = true;@Overridepublic void run() {while (hasTicketFlag) {buyTicket();}System.out.println("票卖完了");}public synchronized void buyTicket() {if (ticket > 0) {System.out.println(Thread.currentThread().getName() + "买到了第" + ticket + "张票");ticket--;} else {hasTicketFlag = false;}}
}

4.同步块

        锁的是需要修改的变量，需要增删改查的对象

实现：

package com.example.threadstudy.safethread;public class SafeBank {public static void main(String[] args) {Account1 account = new Account1(100, "结婚基金");Drawing1 you = new Drawing1(account, 50, "展堂");Drawing1 girlfriend = new Drawing1(account, 100, "sad");you.start();girlfriend.start();}
}//账户
class Account1 {int money;//余额String cardName;//卡名public Account1(int money, String cardName) {this.money = money;this.cardName = cardName;}
}//银行:模拟取款
class Drawing1 extends Thread {Account1 account;//账户int drawingMoney;//取金额int nowMoney;//你手里的钱public Drawing1(Account1 account, int drawingMoney, String name) {super(name);this.account = account;this.drawingMoney = drawingMoney;}//取钱@Overridepublic void run() {//锁的对象就是变量的量,需要增删改查的对象synchronized (account) {//判断是否有钱if (account.money - drawingMoney < 0) {System.out.println(Thread.currentThread().getName() + "余额不足,不能进行取钱");return;}try {Thread.sleep(1000);//放大问题的发生性} catch (InterruptedException e) {e.printStackTrace();}//卡内金额 = 余额-你的钱account.money = account.money - drawingMoney;//你手里的钱nowMoney = nowMoney + drawingMoney;System.out.println(account.cardName + "余额为:" + account.money);//this.getName()==Thread.currentThread().getName()System.out.println(this.getName() + "手里的钱:" + nowMoney);}}
}

5.死锁

实现：

/*** 死锁:多个线程互相抱着对方需要的资源,然后形成僵持* 解决:一个锁只锁一个对象*/
class DeadLock {public static void main(String[] args) {Makeup makeup = new Makeup(0, "灰姑娘");Makeup makeup1 = new Makeup(1, "白雪公主");makeup.start();makeup1.start();}
}//口红
class Lipstick { }
//镜子
class Mirror { }class Makeup extends Thread {//需要的资源只有一份,用static保证只有一份static Lipstick lipstick = new Lipstick();static Mirror mirror = new Mirror();int choice;//选择String girlName;//使用化妆品的人public Makeup(int choice, String girlName) {this.choice = choice;this.girlName = girlName;}@Overridepublic void run() {//化妆try {makeup();} catch (InterruptedException e) {e.printStackTrace();}}private void makeup() throws InterruptedException {if (choice == 0) {synchronized (lipstick) {//获得口红的锁System.out.println(this.girlName + "获得口红的锁");Thread.sleep(1000);synchronized (mirror) {//一秒钟后想获得镜子System.out.println(this.girlName + "获得镜子的锁");}}} else {synchronized (mirror) {//获得口红镜子System.out.println(this.girlName + "获得镜子的锁");Thread.sleep(2000);synchronized (lipstick) {//二秒钟后想获得的锁System.out.println(this.girlName + "获得口红的锁");}}}}
}

解决方式：不要相互占有资源

/*** 死锁:多个线程互相抱着对方需要的资源,然后形成僵持* 解决:一个锁只锁一个对象*/
class DeadLock {public static void main(String[] args) {Makeup makeup = new Makeup(0, "灰姑娘");Makeup makeup1 = new Makeup(1, "白雪公主");makeup.start();makeup1.start();}
}//口红
class Lipstick { }
//镜子
class Mirror { }class Makeup extends Thread {//需要的资源只有一份,用static保证只有一份static Lipstick lipstick = new Lipstick();static Mirror mirror = new Mirror();int choice;//选择String girlName;//使用化妆品的人public Makeup(int choice, String girlName) {this.choice = choice;this.girlName = girlName;}@Overridepublic void run() {//化妆try {makeup();} catch (InterruptedException e) {e.printStackTrace();}}private void makeup() throws InterruptedException {if (choice == 0) {synchronized (lipstick) {//获得口红的锁System.out.println(this.girlName + "获得口红的锁");Thread.sleep(1000);}synchronized (mirror) {//一秒钟后想获得镜子System.out.println(this.girlName + "获得镜子的锁");}} else {synchronized (mirror) {//获得口红镜子System.out.println(this.girlName + "获得镜子的锁");Thread.sleep(2000);}synchronized (lipstick) {//二秒钟后想获得的锁System.out.println(this.girlName + "获得口红的锁");}}}
}
死锁避免办法

6.Lock(锁)

//测试Lock锁
public class Demo32_ThreadLock {public static void main(String[] args) {TestLock testLock = new TestLock();new Thread(testLock).start();new Thread(testLock).start();new Thread(testLock).start();}
}class TestLock implements Runnable {int tickerNums = 10;//定义Lock锁private final ReentrantLock lock = new ReentrantLock();@Overridepublic void run() {while (true) {//加锁try {lock.lock();if (tickerNums <= 0) {break;}try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(tickerNums--);} catch (Exception e) {e.printStackTrace();} finally {//解锁lock.unlock();}}}
}

7.synchroized与Lock对比

五、线程通信问题

生产者消费者模式的问题

1.线程通信方法

2.线程通信问题解决方式

/*** 测试:生产者消费者模型-->利用缓冲区解决:管程法*/
public class ThreadPC {public static void main(String[] args) {SynContainer synContainer = new SynContainer();new Producer(synContainer).start();new Consumer(synContainer).start();}
}//生产者
class Producer extends Thread {//容缓冲区SynContainer container;public Producer(SynContainer container) {this.container = container;}//生产@Overridepublic void run() {for (int i = 0; i < 100; i++) {container.push(new Product(i));System.out.println("生产了" + i + "件产品");}}
}//消费者
class Consumer extends Thread {//容缓冲区SynContainer container;public Consumer(SynContainer container) {this.container = container;}//消费@Overridepublic void run() {for (int i = 0; i < 100; i++) {System.out.println("消费了-->" + container.pop().id + "件产品");}}
}//产品
class Product {int id;//产品编号public Product(int id) {this.id = id;}
}//缓冲区
class SynContainer {//需要一个容器大小Product[] products = new Product[10];//容器计数器int count = 0;//生产者放入产品public synchronized void push(Product product) {//如果容器满了,需要等待消费者消费/*如果是if的话，假如消费者1消费了最后一个，这是index变成0此时释放锁被消费者2拿到而不是生产者拿到，这时消费者的wait是在if里所以它就直接去消费index-1下标越界，如果是while就会再去判断一下index得值是不是变成0了*/while (count == products.length) {//通知消费者消费,等待生产try {this.wait();} catch (InterruptedException e) {e.printStackTrace();}}//如果没有满,需要丢入产品products[count] = product;count++;//通知消费者消费this.notifyAll();}//消费者消费产品public synchronized Product pop() {//判断是否能消费while (count <= 0) {//等待生产者生产try {this.wait();} catch (InterruptedException e) {e.printStackTrace();}}//如果可以消费count--;Product product = products[count];//吃完了 通知生产者生产this.notifyAll();return product;}
}


/*** 测试:生产者消费者模型-->利用缓冲区解决:管程法*/
public class ThreadPC {public static void main(String[] args) {SynContainer synContainer = new SynContainer();new Producer(synContainer).start();new Consumer(synContainer).start();}
}//生产者
class Producer extends Thread {//容缓冲区SynContainer container;public Producer(SynContainer container) {this.container = container;}//生产@Overridepublic void run() {for (int i = 0; i < 100; i++) {container.push(new Product(i));System.out.println("生产了" + i + "件产品");}}
}//消费者
class Consumer extends Thread {//容缓冲区SynContainer container;public Consumer(SynContainer container) {this.container = container;}//消费@Overridepublic void run() {for (int i = 0; i < 100; i++) {System.out.println("消费了-->" + container.pop().id + "件产品");}}
}//产品
class Product {int id;//产品编号public Product(int id) {this.id = id;}
}//缓冲区
class SynContainer {//需要一个容器大小Product[] products = new Product[10];//容器计数器int count = 0;//生产者放入产品public synchronized void push(Product product) {//如果容器满了,需要等待消费者消费/*如果是if的话，假如消费者1消费了最后一个，这是index变成0此时释放锁被消费者2拿到而不是生产者拿到，这时消费者的wait是在if里所以它就直接去消费index-1下标越界，如果是while就会再去判断一下index得值是不是变成0了*/while (count == products.length) {//通知消费者消费,等待生产try {this.wait();} catch (InterruptedException e) {e.printStackTrace();}}//如果没有满,需要丢入产品products[count] = product;count++;//通知消费者消费this.notifyAll();}//消费者消费产品public synchronized Product pop() {//判断是否能消费while (count <= 0) {//等待生产者生产try {this.wait();} catch (InterruptedException e) {e.printStackTrace();}}//如果可以消费count--;Product product = products[count];//吃完了 通知生产者生产this.notifyAll();return product;}
}

六、线程池

public class ThreadPool {public static void main(String[] args) {ExecutorService executorService = Executors.newFixedThreadPool(10);//执行executorService.execute(new testThreadPool());executorService.execute(new testThreadPool());executorService.execute(new testThreadPool());executorService.execute(new testThreadPool());executorService.execute(new testThreadPool());executorService.execute(new testThreadPool());//关闭连接executorService.shutdown();}
}class testThreadPool implements Runnable {@Overridepublic void run() {System.out.println(Thread.currentThread().getName());}
}

至此鸣谢：狂神说多线程笔记整理_狂神多线程笔记-CSDN博客

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