Java多线程编程中的并发安全问题及解决方法

public class DeadLookTest {
    private static Object o1 = new Object();
    private static Object o2 = new Object();
    public void fastLock() throws InterruptedException {
        synchronized(o1){
            Thread.sleep(2000);
            System.out.println("fast");
            synchronized (o2){
                System.out.println("----");
            }
        }
    }
    public void postLock() throws InterruptedException {
        synchronized(o2){
            Thread.sleep(2000);
            System.out.println("post");
            synchronized (o1){
                System.out.println("----");
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        DeadLookTest deadlook = new DeadLookTest();
        // 新开一个线程去调用其中一个方法
        new Thread(() -> {
            try {
                deadlook.postLock();
            } catch (InterruptedException e) {
            }
        }).start();
        deadlook.fastLock();
    }
}

private static void businessDo(Object first,Object second) throws InterruptedException {
    String threadName = Thread.currentThread().getName();
    synchronized (first){
        System.out.println(threadName + " get first");
        Thread.sleep(1000);
        synchronized (second){
            System.out.println(threadName + " get second");
        }
    }
}
// 然后两个线程，在调用的时候传递的参数顺序却不一样
businessDo(No1,No2);
businessDo(No2,No1);

public class SafeOperate {
    private static Object No13 = new Object();//第一个锁
    private static Object No14 = new Object();//第二个锁
    private static Object tieLock = new Object();//第三把锁
    public void transfer(Object first,Object second) throws InterruptedException {
        int firstHash = System.identityHashCode(first);
        int secondHash = System.identityHashCode(second);
        if(firstHash<secondHash){
            synchronized (first){
                System.out.println(Thread.currentThread().getName()+" get "+first);
                Thread.sleep(100);
                synchronized (second){
                    System.out.println(Thread.currentThread().getName()+" get "+second);
                }
            }
        }else if(secondHash<firstHash){
            synchronized (second){
                System.out.println(Thread.currentThread().getName()+" get"+second);
                Thread.sleep(100);
                synchronized (first){
                    System.out.println(Thread.currentThread().getName()+" get"+first);
                }
            }
        }else{
            // 万一两个对象的hash值一样，那么就引入第三把锁，谁先抢到第三把锁就去进行前两两把锁的加锁
            synchronized (tieLock){
                synchronized (first){
                    synchronized (second){
                        System.out.println(Thread.currentThread().getName()+" get"+first);
                        System.out.println(Thread.currentThread().getName()+" get"+second);
                    }
                }
            }
        }
    }
}

while(true){
    if(No13.tryLock()){
        System.out.println(threadName +" get 13");
        // 如果没有拿到No14的锁，那么No13的锁也释放
        try{
            if(No14.tryLock()){
                try{
                    System.out.println(threadName  +" get 14");
                    System.out.println("zhouYuDo do work------------");
                    break;
                }finally{
                    No14.unlock();
                }
            }
        }finally {
            No13.unlock();
        }
    }
    // 如果不加休眠机制，那么就比较容易产生活锁
    Thread.sleep(1000);
}

public class HungrySingleton {
    //创建 SingletonHungry 的一个对象
    private static volatile HungrySingleton instance;
    // 让构方法私有，这样该类就不会被其它类实例化
    private HungrySingleton() {
    }
    //获取唯一可用的对象
    public static HungrySingleton getInstance() {
        if(null == instance) { 
            synchronized{
                if(null == instance) { 
                    instance = new LazySingleton();
                }
            }
        }
    	return instance;
    }
}