ThreadLocal原理与模拟

public class ThreadLocal1 {
    private static Dictionary<Thread, Integer> map;

    public static void main(String[] args) {
        map = new Hashtable<Thread, Integer>();
        for (int i = 0; i < 2; i++) {
            new Thread(new Runnable() {

                public void run() {
                    int data = new Random().nextInt();
                    map.put(Thread.currentThread(), data);
                    System.out.println(Thread.currentThread() + ", data:"
                            + data);
                    new A().show();
                    new B().show();
                }
            }).start();
        }
    }

    static class A {
        public void show() {
            System.out.println(Thread.currentThread() + "调用A, data:" + map.get(Thread.currentThread()));
        }
    }

    static class B {
        public void show() {
            System.out.println(Thread.currentThread() + "调用B, data:" + map.get(Thread.currentThread()));
        }
    }
}

public class ThreadLocal2 {

    public static void main(String[] args) {
        for (int i = 0; i < 2; i++) {
            new Thread(new Runnable() {

                public void run() {
                    int data = new Random().nextInt(1000);
                    Student instance = Student.getInstance();
                    instance.setName(data + "");
                    instance.setAge(data);
                    System.out.println(Thread.currentThread() + ", name:"
                            + instance.getName() + ",age:" + instance.getAge());
                    new A().show();
                    new B().show();
                }
            }).start();
        }
    }

    static class A {
        public void show() {
            Student instance = Student.getInstance();
            System.out.println(Thread.currentThread() + "调用A, name:"
                    + instance.getName()+",age:"+instance.getAge());
        }
    }

    static class B {
        public void show() {
            Student instance = Student.getInstance();
            System.out.println(Thread.currentThread() + "调用B, name:"
                    + instance.getName()+",age:"+instance.getAge());
        }
    }
}

class Student {

    // private Student instance;
    private static ThreadLocal<Student> threadInstance = new ThreadLocal<Student>();

    private Student() {
    }

    public static Student getInstance() {
    
        Student instance = threadInstance.get();
        if (instance == null) {
            instance = new Student();
            threadInstance.set(instance);
        }
        return instance;
    }

    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

}