线程基础

线程的生命周期

线程的启动

package com.thread.demo;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class ThreadByRunable {
    private static class ThreadByThread extends Thread{

        @Override
        public void run() {
            System.out.println("我是继承Thread接口的线程");
        }
        
    }
    private static class RunableThread implements Runnable{

        @Override
        public void run() {
            System.out.println("我是实现runable接口的线程");
        }
        
    }
    /*实现callable线程，可以有返回值*/
    private static class Callabled implements Callable<String> {

        @Override
        public String call() throws Exception {
            System.out.println("我是实现callable接口的线程，我的返回值类型是<String>");
            return "CallableSuccess";
        }
        
    }
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        ThreadByThread t = new ThreadByThread();
        t.start();
        
        RunableThread threadByRunable = new RunableThread();
        new Thread(threadByRunable).start();
        Thread t1 = new Thread(threadByRunable);
        t1.interrupt();
        
        Callabled call = new Callabled();
        FutureTask<String> futureTask = new FutureTask<>(call);
        new Thread(futureTask).start();
        System.out.println(futureTask.get());
        
    }
    
}

线程自然终止：自然执行完或抛出未处理异常

终止线程的方法

interrupt() 方法中断一个线程，并不是强行关闭这个线程，只是跟这个线程打个招呼，将线程的中断标志位置为true，线程是否中断，由线程本身决定。

isInterrupted() 判定当前线程是否处于中断状态。

static方法interrupted() 判定当前线程是否处于中断状态，同时中断标志位改为false。

java的线程是协作式的，不是抢占式，因此，想安全的中断一个线程，使用interrupt()只是告诉线程需要来中断了，但是，如果线程中对interrupt没有进行判定，没有使用isInterrupted()，那么该线程还是会一直运行，如下demo

package com.thread.demo;


public class ThreadByThread {
    private static class UseThread extends Thread {
        @Override
        public void run() {
            try {
                while(!interrupted()){
                    System.out.println(Thread.currentThread().getName()
                            +"我是继承thread的线程");
                }
                System.out.println(Thread.currentThread().getName()
                        +"中断的状态是"+isInterrupted());
            }finally{
                System.out.println("over");
            }
            
        }
    }
    private static class UseThread2 extends Thread {
        @Override
        public void run() {
            try {
                while(true){//此处没有对是否中断进行识别，那么当主方法中调用interrupt()时，该线程不会被中断
                    System.out.println(Thread.currentThread().getName()
                            +"我是继承thread的线程");
                }
            }finally{
                System.out.println("over");
            }
            
        }
    }
    private static class RunableThread implements Runnable{

        @Override
        public void run() {
            String threadName = Thread.currentThread().getName();
            while(!Thread.currentThread().isInterrupted()) {
                System.out.println(threadName+" is run!");
            }
            System.out.println(threadName+" interrput flag is "
                    +Thread.currentThread().isInterrupted());
        }        
        
    }
    public static void main(String[] args) throws InterruptedException {
        UseThread useThread = new UseThread();
        //设置为守护线程，默认为用户线程
        useThread.setDaemon(true);
        useThread.start();
        UseThread.sleep(5);
        useThread.interrupt();
        
        
        UseThread2 useThread2 = new UseThread2();
        //设置为守护线程，默认为用户线程
        useThread2.setDaemon(true);
        useThread2.start();
        UseThread2.sleep(5);
        useThread2.interrupt();
        
        RunableThread threadByRunable = new RunableThread();
        Thread t1 = new Thread(threadByRunable,"111");
        t1.start();
        Thread.sleep(20);
        t1.interrupt();
        
    }

}

 当线程中catch到InterruptedException时，isInterrupt()会初始化为false

public class HasInterrputException {
    
    private static class UseThread extends Thread{
        
        public UseThread(String name) {
            super(name);
        }
        
        @Override
        public void run() {
            String threadName = Thread.currentThread().getName();
            while(isInterrupted()) {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    System.out.println(threadName+" interrput flag is "
                            +isInterrupted());
                    interrupt();
                    e.printStackTrace();
                }
                System.out.println(threadName);                
            }
            System.out.println(threadName+" interrput flag is "
                    +isInterrupted());
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Thread endThread = new UseThread("HasInterrputEx");
        endThread.start();
        Thread.sleep(500);
        endThread.interrupt();
        

    }

}

守护线程：与主线程生命周期同步，finally不一定会执行，GC就是典型的守护线程

public class DaemonThread {
    private static class  DaemonDemo extends Thread{
        @Override
        public void run() {
            try {
                while (!isInterrupted()) {
                    System.out.println(Thread.currentThread().getName()
                            + " I am extends Thread.");
                }
                System.out.println(Thread.currentThread().getName() 
                        + " interrupt flag is " + isInterrupted());
            } finally {
                System.out.println("...........finally");
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        DaemonDemo daemonDemo = new DaemonDemo();
//        daemonDemo.setDaemon(true);
        daemonDemo.start();
        Thread.sleep(10);
        daemonDemo.interrupt();
        
    }

}

main方法中的 setDaemon(true)放开，finally不会执行

线程间的共享

synchronized内置锁：

1.对象所锁：有synchronize没有static修饰词的方法

2.类锁：有synchronize有static修饰词的方法

自己的理解：对象锁，锁的是对象，必须要是同一个new 出来的对象，才会共享一个线程，排队执行方法；类锁，一种特殊的对象锁，锁的是类，所以不管new多少个类，但是共享的还是一个锁，所以都会共享一个线程，demo中主要根据main方法中的new出来的情况，看打印的顺序，同时打出来就是没有共享线程，一个一个的打出来就是共享了

public class SynClzAndInst {
    
    //使用类锁的线程
    private static class SynClass extends Thread{
        @Override
        public void run() {
            System.out.println("TestClass 开始运行了...");
            synClass();
        }
    }

  //使用对象锁的线程
    private static class InstanceSyn implements Runnable{
        private SynClzAndInst synClzAndInst;

        public InstanceSyn(SynClzAndInst synClzAndInst) {
            this.synClzAndInst = synClzAndInst;
        }

        @Override
        public void run() {
            System.out.println("InstanceSyn is running..."+synClzAndInst);
            synClzAndInst.instance();
        }
    }

  //使用对象锁的线程
    private static class Instance2Syn implements Runnable{
        private SynClzAndInst synClzAndInst;

        public Instance2Syn(SynClzAndInst synClzAndInst) {
            this.synClzAndInst = synClzAndInst;
        }
        @Override
        public void run() {
            System.out.println("Instance2Syn is running..."+synClzAndInst);
            synClzAndInst.instance2();
        }
    }

    //锁对象
    private synchronized void instance(){
        SleepTools.second(3);
        System.out.println("instance is going..."+this.toString());
        SleepTools.second(3);
        System.out.println("instance ended "+this.toString());
    }
    
    //锁对象
    private synchronized void instance2(){
        SleepTools.second(3);
        System.out.println("instance2 is going..."+this.toString());
        SleepTools.second(3);
        System.out.println("instance2 ended "+this.toString());
    }

    //类锁，实际是锁类的class对象
    private static synchronized void synClass(){
        SleepTools.second(1);
        System.out.println("synClass 在运行...");
        SleepTools.second(1);
        System.out.println("synClass 运行完毕");
    }

    public static void main(String[] args) {
//        //实例一个对象
//        SynClzAndInst synClzAndInst = new SynClzAndInst();
//        //把对象交给一个线程（runnable的启动）
//        Thread t1 = new Thread(new InstanceSyn(synClzAndInst));
//        //实例另一个对象
//        SynClzAndInst synClzAndInst2 = new SynClzAndInst();
        //t2中放入的实例对象和t1不同，那就不是共享线程，是两个不同的锁，会同时打印
//        Thread t2 = new Thread(new Instance2Syn(synClzAndInst2));
        //如果t2中放入的对象和t1是同一个，那就是共享线程，是同一个对象锁，会排队打印
//        Thread t2 = new Thread(new Instance2Syn(synClzAndInst));
//        t1.start();
//        t2.start();

        //new 两个类（这个对象那中的内部类），虽然new出来是两个不同名的内部类，但是类锁却是同一个，所以会排队打印
        SynClass synClass = new SynClass();
        synClass.start();
        SynClass synClass2 = new SynClass();
        synClass2.start();
        //线程休眠的工具方法
        SleepTools.second(1);
    }
}

SleepTools的代码

public class SleepTools {
    
    /**
     * 按秒休眠
     * @param seconds 秒数
     */
    public static final void second(int seconds) {
        try {
            TimeUnit.SECONDS.sleep(seconds);
        } catch (InterruptedException e) {
        }
    }
    
    /**
     * 按毫秒数休眠
     * @param seconds 毫秒
     */
    public static final void ms(int seconds) {
        try {
            TimeUnit.MILLISECONDS.sleep(seconds);
        } catch (InterruptedException e) {
        }
    }
}

 线程变量ThreadLocal

可以理解为是个map，类型 Map<Thread,Integer>

public class UseThreadLocal {
    
    //可以理解为 一个map，类型 Map<Thread,Integer>
    static ThreadLocal<Integer> threadLaocl = new ThreadLocal<Integer>(){
        @Override
        protected Integer initialValue() {
            return 1;
        }
    };

    /**
     * 运行3个线程
     */
    public void StartThreadArray(){
        Thread[] runs = new Thread[3];
        for(int i=0;i<runs.length;i++){
            runs[i]=new Thread(new TestThread(i));
        }
        for(int i=0;i<runs.length;i++){
            runs[i].start();
        }
    }
    
    /**
     *类说明：测试线程，线程的工作是将ThreadLocal变量的值变化，并写回，看看线程之间是否会互相影响
     */
    public static class TestThread implements Runnable{
        int id;
        public TestThread(int id){
            this.id = id;
        }
        public void run() {
            System.out.println(Thread.currentThread().getName()+":start");
            Integer s = threadLaocl.get();//获得变量的值
            s = s+id;
            threadLaocl.set(s);
            System.out.println(Thread.currentThread().getName()+":"
            +threadLaocl.get());
            //threadLaocl.remove();
        }
    }

    public static void main(String[] args){
        UseThreadLocal test = new UseThreadLocal();
        test.StartThreadArray();
    }
}
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 等待和通知（wait()/notify(),notifyAll()）

等待方：wait()

1、 获取对象的锁；

2、 循环里判断条件是否满足，不满足调用wait方法，

3、 条件满足执行业务逻辑

通知方来说:notify(),notifyAll()

1、 获取对象的锁；

2、 改变条件

3、 通知所有等待在对象的线程

尽量选用notifyAll()

一个烂大街的demo，打印1A2B3C...

public class AddNumAndWords {
    private static class demoThread1 extends Thread{
        private AddNumAndWords add;
        public demoThread1(AddNumAndWords add) {
            this.add=add;
            
        }
        @Override
        public void run() {
            try {
                synchronized (add) {
                    for(int i=0;i<26;i++){
                        System.out.print(i);
                        add.notifyAll();
                        add.wait();
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    private static class demoThread2 extends Thread{
        private AddNumAndWords add;
        public demoThread2(AddNumAndWords add) {
            this.add=add;
            
        }
        @Override
        public void run() {
            try {
                synchronized (add) {
                    for(int i=0;i<26;i++){
                        add.wait();
                        char ss = (char) (65+i);
                        System.out.print(String.valueOf(ss));
                        add.notifyAll();
                        
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        AddNumAndWords add = new AddNumAndWords();
        Thread t1 = new demoThread2(add);
        Thread t2 = new demoThread1(add);
        t1.start();
        t2.start();
        
        try {
            t1.join();
            t2.join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        
    }

}
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原文地址：https://www.cnblogs.com/1027395552lyd/p/10466222.html