Java_多线程(创建/同步锁/等待唤醒机制/线程池/AsyncTask)

Java_多线程(创建/同步锁/等待唤醒机制/线程池/AsyncTask)

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本文由 Luzhuo 编写,转发请保留该信息.
原文: http://blog.youkuaiyun.com/Rozol/article/details/77344792

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本文讲解了: 线程的创建 / 同步锁机制 / 等待唤醒机制 / 线程池 / Android的AsyncTask源码分析

线程的创建

创建子线程大约可分为4中方式

public class Test {
   
    public static void main(String[] args) {
        // 方式一: 继承Thread类
        run1();

        // 方式二: 重写Thread的run方法
        run2();

        // 方式三: 实现Runnable接口
        run3();

        // 方式四: 实现Runnable接口2
        run4();
    }


    /**
     * 方式一: 继承Thread类
     */
    private static void run1() {
        MyThreadClass thread1_1 = new MyThreadClass();
        MyThreadClass thread1_2 = new MyThreadClass("thread 1_2");

        thread1_1.setName("thread 1_1");

        thread1_1.start();
        thread1_2.start();      
    }

    /**
     * 方式二: 重写Thread的run方法
     */
    private static void run2() {
        new Thread("thread 2"){
            public void run() {
                for (int x = 0; x < 100; x++) {
                    System.out.println(Thread.currentThread().getName() + ": " + x);
                }
            };
        }.start();      
    }

    /**
     * 方式二: 实现Runnable接口
     */
    private static void run3() {
        Thread thread2_1 = new Thread(new MyRunnable());
        thread2_1.setName("thread 3_1");
        thread2_1.start();

        Thread thread2_2 = new Thread(new MyRunnable(), "thread 3_2");
        thread2_2.start();      
    }

    /**
     * 方式三: 实现Runnable接口2
     */
    private static void run4() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int x = 0; x < 100; x++) {
                    System.out.println(Thread.currentThread().getName() + ": " + x);
                }
            }
        }, "thread 4").start();     
    }
}

public class MyThreadClass extends Thread{
   

    public MyThreadClass(){};

    public MyThreadClass(String name){
        super(name);
    };

    @Override
    public void run(){ //继承Thread类并重写run()方法
        for(int x = 0; x < 100; x++){
            //public final String getName(); //返回该线程的名称
            System.out.println(getName() + ": " + x);
        }
    }
}

public class MyRunnable implements Runnable{
   
    @Override
    public void run() {
        for (int x = 0; x < 100; x++) {
            //public static Thread currenthread(); //返回对当前正在执行的线程对象的引用
            System.out.println(Thread.currentThread().getName() + ": " + x);
        }
    }
}

线程的同步锁

同步锁实现方式

/**
 * 同步锁的几种实现放方式
 * 区别: 
 *      Synchronized: 采用CPU悲观锁机制(JVM执行), 线程是独占的, 当很多线程进程锁时会引起CPU频繁切换而影响性能
 *      Lock: java写的乐观锁, 每次不加锁假设没有冲突去执行, 如果发生冲突则重试
 * @author Luzhuo
 */
public class Test {
   
    public static void main(String[] args) {
        // 方式1: 同步代码块
        SynchronizedBlock block = new SynchronizedBlock();

        Thread thread1_1 = new Thread(block, "1号窗口");
        Thread thread1_2 = new Thread(block, "2号窗口");

        thread1_1.start();
        thread1_2.start();

        // 方式2: 同步方法
        SynchronizedMethod method = new SynchronizedMethod();

        Thread thread2_1 = new Thread(method, "1号窗口");
        Thread thread2_2 = new Thread(method, "2号窗口");

        thread2_1.start();
        thread2_2.start();

        // 方式3: 静态同步方法
        SynchronizedStaticMethod staticMethod = new SynchronizedStaticMethod();

        Thread thread3_1 = new Thread(staticMethod, "1号窗口");
        Thread thread3_2 = new Thread(staticMethod, "2号窗口");

        thread3_1.start();
        thread3_2.start();

        // 方式4: Lock锁
        LockBlock lockBlock = new LockBlock();

        Thread thread4_1 = new Thread(lockBlock, "1号窗口");
        Thread thread4_2 = new Thread(lockBlock, "2号窗口");

        thread4_1.start();
        thread4_2.start();

        // ==========================================================

        // 数据安全访问的几种方式
        DataSecurity data = new DataSecurity();

        Thread thread5_1 = new Thread(data, "thread 1");
        Thread thread5_2 = new Thread(data, "thread 2");

        thread5_1.start();
        thread5_2.start();
    }
}

/**
 * 同步代码块
 * @author Luzhuo
 */
public class SynchronizedBlock implements Runnable{
   
    private static int x = 100; // 票的数量
    private Object obj = new Object();

    @Override
    public void run() {
        while (true) {
            syncBlock();
        }
    }

    /**
     * 方式1: 同步代码块, 锁对象:任意对象
     */
    public void syncBlock() {
        // synchronized代码同步锁
        synchronized (obj) { // 锁对象是new Object(); 
            if (x > 0) {
                try {
                    // public static void sleep(long millis); // 以指定毫秒数内暂停线程
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + "正在出售第 " + (x--) + " 张票");
            }
        }
    }
}

/**
 * 同步方法
 * @author Luzhuo
 */
public class SynchronizedMethod implements Runnable{
   
    private static int x = 100; // 票的数量

    @Override
    public void run() {
        while(true){
            syncMethod();
        }
    }

    /**
     * 方式2: 同步方法: 锁对象:this
     */
    private synchronized void syncMethod() {  //锁对象是 this
        if (x > 0) {
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "正在出售第 " + (x--) + " 张票");
        }
    }
}

/**
 * 静态同步方法
 * @author Luzhuo
 *
 */
public class SynchronizedStaticMethod implements Runnable{
   
    private static int x = 100; // 票的数量

    @Override
    public void run() {
        while(true){
            syncStaticMethod();
        }
    }

    /**
     * 方式3: 静态同步方法: 锁对象: 类.class 字节码文件对象
     */
    private static synchronized void syncStaticMethod(){ //锁对象是 Ticket.class
        if (x > 0) {
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "正在出售第 " + (x--) + " 张票");
        }
    }
}

/**
 * Lock是Java5之后加入的
 * @author Luzhuo
 */
public class LockBlock implements Runnable{
   
    private int x = 100; // 票的数量

    @Override
    public void run() {
        while (true) {
            lockBlock();
        }
    }

    // 定义一个锁对象
    private final Lock lock = new ReentrantLock();

    /**
     * 方式4: Lock锁代码块
     */
    public void lockBlock() {
        // void lock(); //获取锁
        lock.lock();

        try{

            if (x > 0) {
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + "正在出售第 " + (x--) + " 张票");
            }

        }finally {
            // void unlock(); //释放锁
            lock.unlock();
        }
    }
}

死锁

/**
 * 死锁的案例
 * 死锁的产生: 线程1拿着objA的锁去获取objB的锁, 线程2拿着objB的锁去获取objA的锁, 两者互不相让就产生了死锁
 * @author Luzhuo
 */
public class 死锁{
   
    public static void main(String[] args) {
        死锁.DieLock d1 = new 死锁.DieLock(true);
        死锁.DieLock d2 = new 死锁.DieLock(false);
        d1.start();
        d2.start();
    }

    public static class DieLock extends Thread{
   
        private boolean flag;

        public DieLock(boolean flag){
            this.flag = flag;
        }

        public void run() {
            if(flag){
                while(true){
                    synchronized (Mylock.objA) {
                        System.out.println("if objA");
                        synchronized (Mylock.objB) {
                            System.out.println("if objB");
                        }
                    }
                }
            }else{
                while(true){
                    synchronized (Mylock.objB) {
                        System.out.println("else objB");