ThreadLocal源代码1

public class ThreadLocalTrxt {
    static ThreadLocal<Object> x1 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x2 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x3 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x4 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x5 = new ThreadLocal<Object>();

    public static void main(String[] args) {
        for (int i = 0; i < 2; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    for(int i = 0; i<5; i++) {
                        x1.set(i); //把x1设置到这个线程的threadLocals里面的table里面的Entry里面的referent里面去，还有i=0
                        x2.set(i);
                        x3.set(i);
                        x4.set(i);
                        x5.set(i);
                    }
                    Thread t = Thread.currentThread();
                    ThreadLocal<Object> x6 = new ThreadLocal<Object>();
                    x6.remove();
                    x1.remove();
                    x2.remove();
                    x3.remove();
                    x4.remove();
                    x5.remove();
                }
            }).start();
        }
    }
}

public class Test {

    public static void main(String[] args) {
        AtomicInteger hashCode = new AtomicInteger();
        int hash_increment = 0x61c88647;
        int size = 32;
        List <Integer> list = new ArrayList <> ();
        for (int i = 0; i < size; i++) {
            System.out.println(hashCode);
            hashCode.getAndAdd(hash_increment);
            System.out.println(hashCode);
            System.out.println(hashCode.intValue() & (size - 1));
            list.add(hashCode.intValue() & (size - 1));
        }
        System.out.println("original:" + list);
        Collections.sort(list);
        System.out.println("sort:    " + list);
        System.out.println(hash_increment);
    }
}

public class ThreadLocalTrxt {
    static ThreadLocal<Integer> x = new ThreadLocal<Integer>();
    public static void main(String[] args) {
        for (int i = 0; i < 2; i++) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    int s = new Random().nextInt();
                    x.set(s);     //   ThreadLocal 设置值的时候，自动跟线程关联
                    System.out.println(x.get());    //  ThreadLocal 取值的时候，自动跟线程关联
                }
            }).start();
        }
    }
}

public void set(T value) {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);  // 返回null
        if (map != null)
            map.set(this, value);
        else
            createMap(t, value);
    }
threadLocals是ThreadLocalMap在线程Thread里面
ThreadLocalMap getMap(Thread t) {
        return t.threadLocals;  //  返回线程的threadLocals，是一个ThreadLocalMap类型，只不过这个类型在ThreadLocal里面定义
    }

void createMap(Thread t, T firstValue) {
        t.threadLocals = new ThreadLocalMap(this, firstValue);    //this是ThreadLocal，调用x.set(s);的x
    }

public T get() {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null) {
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null) {
                @SuppressWarnings("unchecked")
                T result = (T)e.value;
                return result;
            }
        }
        return setInitialValue();
    }

 ThreadLocal设置值是设置到这个线程的threadLocals属性里面去了，并且ThreadLocal自己也在threadLocals里面。多个线程共用这个ThreadLocal。

ThreadLocalMap的key是ThreadLocal，Value是set方法设置进来的值。
Entry是ThreadLocalMap的内部类，ThreadLocal和value2个属性组成。

线程初始化时候：

public class ThreadLocalTrxt {
    static ThreadLocal<Object> x1 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x2 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x3 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x4 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x5 = new ThreadLocal<Object>();
    static ThreadLocal<Object> x6 = new ThreadLocal<Object>();

    public static void main(String[] args) {
        for (int i = 0; i < 2; i++) {
            new Thread(new Runnable() {//2个线程调用，则2个线程共享x1,x2,x3,x4,x5,x6。但是ThreadLocal里面没有属性（只是充当一个key），2个线程修改的时候，
                                    //修改的是线程内部的threadLocals。Thread和ThreadLocal是在一个包下的。不同线程相同的key（ThreadLocal）得到的可以是不同的value。
                @Override
                public void run() {
                    for(int i = 0; i<5; i++) {
                    x1.set(i); //把x1设置到这个线程的threadLocals里面的table里面的Entry里面的referent里面去，还有i=0
                    x2.set(i); //  重复调用会覆盖
                    x3.set(i);
                    x4.set(i);
                    x5.set(i);
                    x6.set(i);
                    }
                    Thread t = Thread.currentThread();
                    System.out.println(x1.get());
                    x1.remove();
                }
            }).start();
        }
    }
}

ThreadLocal无法解决线程安全问题。也就是说ThreadLocal是被各个线程共享的。