ThreadLocal源代碼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設置到這個線程的threadLocals裏面的table裏面的Entry裏面的referent裏面去，還有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 設置值的時候，自動跟線程關聯
                    System.out.println(x.get());    //  ThreadLocal 取值的時候，自動跟線程關聯
                }
            }).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在線程Thread裏面
ThreadLocalMap getMap(Thread t) {
        return t.threadLocals;  //  返回線程的threadLocals，是一個ThreadLocalMap類型，只不過這個類型在ThreadLocal裏面定義
    }

void createMap(Thread t, T firstValue) {
        t.threadLocals = new ThreadLocalMap(this, firstValue);    //this是ThreadLocal，調用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設置值是設置到這個線程的threadLocals屬性裏面去了，而且ThreadLocal本身也在threadLocals裏面。多個線程共用這個ThreadLocal。

ThreadLocalMap的key是ThreadLocal，Value是set方法設置進來的值。
Entry是ThreadLocalMap的內部類，ThreadLocal和value2個屬性組成。

 

 線程初始化時候：

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個線程調用，則2個線程共享x1,x2,x3,x4,x5,x6。可是ThreadLocal裏面沒有屬性（只是充當一個key），2個線程修改的時候，
                                    //修改的是線程內部的threadLocals。Thread和ThreadLocal是在一個包下的。不一樣線程相同的key（ThreadLocal）獲得的能夠是不一樣的value。
                @Override
                public void run() {
                    for(int i = 0; i<5; i++) {
                    x1.set(i); //把x1設置到這個線程的threadLocals裏面的table裏面的Entry裏面的referent裏面去，還有i=0
                    x2.set(i); //  重複調用會覆蓋
                    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沒法解決線程安全問題。也就是說ThreadLocal是被各個線程共享的。