ThreadLocal使用方法

[hz90]

/**

• 1，ThreadLocal类作用：创建一个变量，此变量只能被当前线程访问
• 如果一个类中有ThreadLocal变量，如果有两个线程访问该类，
• 他们也只能访问自己线程的ThreadLocal变量
• 2，每个线程只能访问自己的ThreadLocal变量
• 通过ThreadLocal.set()方法设置值
• 通过Thread.get()方法获取值
• 3，ThreadLoca</> 支持泛型
• 4，如何初始化，重写ThreadLoca的initialValue()方法，指定初始值

• 5， ThreadLoca只是起到线程间变量隔离的作用 实现原理，、 每个Thread会维持一个ThreadLocalMap，ThreadLocalMap中的key是ThreadLocal，value是要存的值，也就是ThreadLocal通过set()方法设置的值

  / public class TestThreaLocal { //创建ThreadLocal变量 private ThreadLocal testt = new ThreadLocal(); private ThreadLocal stringThreadLocal = new ThreadLocal() { @Override protected String initialValue() { return "hello"; } }; public static void main(String[] args){ TestRunnable testThreaLocal=new TestRunnable(); Thread thread=new Thread(testThreaLocal); Thread thread1=new Thread(testThreaLocal); thread.start(); thread1.start(); } } class TestRunnable implements Runnable{ private ThreadLocal threadLocal = new ThreadLocal(); @Override public void run() { threadLocal.set((int) (Math.random() 1000D)); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(threadLocal.get()); } }

---

import org.apache.commons.lang3.RandomUtils;

import java.util.HashMap; import java.util.Map;

public class TestThreaLocalSelf { private static Map<Thread, Integer> threadIntegerHashMap = new HashMap<Thread, Integer>();

public static void main(String[] args) {
    for (int i = 0; i < 2; i++) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                Integer random= RandomUtils.nextInt(1,100);
                System.out.println("class main" + "Thread:" +
                        Thread.currentThread().getName() + "data:"
                        +random);
                threadIntegerHashMap.put(Thread.currentThread(),random);
                new A().print();
                new B().print();
            }
        }).start();
    }
}

static class A {
    public void print() {
        System.out.println("class A" + "Thread:" +
                Thread.currentThread().getName() + "data:"
                + threadIntegerHashMap.get(Thread.currentThread()));
        try {
            Thread.sleep(50);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
static class B {
    public void print() {
        System.out.println("class B" + "Thread:" +
                Thread.currentThread().getName() + "data:"
                + threadIntegerHashMap.get(Thread.currentThread()));
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

} class mainThread:Thread-1data:75 class mainThread:Thread-0data:94 class AThread:Thread-0data:94 class AThread:Thread-1data:75 class BThread:Thread-1data:75 class BThread:Thread-0data:94

---