ThreadLocal 实现线程内共享变量

package com.cn.gbx;

import java.util.Date;
import java.util.Random;
import java.util.Timer;
import java.util.TimerTask;

public class TestThread {
	static class A{
		public void get() {
			User user = User.getInstance();
			System.out.println("A from " + Thread.currentThread().getName() + " get data:" + user.getName() + " : " + user.getPassword());
		}
	}
	static class B{
		public void get(){
			User user = User.getInstance();
			System.out.println("B from " + Thread.currentThread().getName() + " get data:" + user.getName() + " : " + user.getPassword());
		}
	}
	public static void main(String[] args) {
		for (int i = 0; i < 2; ++i) {
			new Thread(
				new Runnable() {
					@Override
					public void run() {
						int data = new Random().nextInt();
						System.out.println(Thread.currentThread().getName() + " : data = " + data);
						User.getInstance().setName("name:" + data);
						User.getInstance().setPassword("p:" + data);
						new A().get();
						new B().get();
						//A,B 模块得到的都是与本线程相关联的数据， 例如数据库connection等等
					}
				}
			).start();
		}
	}
}

class User{

	//类似单例的懒汉模式  其实ThreadLocal 就是一个Map只不过是自动将key设为本地线程
	private static ThreadLocal<User> threadLocal = new ThreadLocal<User>();
	private User() {}
	public static User getInstance() {
		User user = threadLocal.get();
		if (user == null) {
			user = new User();
			threadLocal.set(user);
		}
		return user;
	}

	private String name;
	private String password;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
}
输出：

Thread-1 : data = 1362065454
Thread-0 : data = 1208952694
A from Thread-0 get data:name:1208952694 : p:1208952694
A from Thread-1 get data:name:1362065454 : p:1362065454
B from Thread-1 get data:name:1362065454 : p:1362065454
B from Thread-0 get data:name:1208952694 : p:1208952694