线程范围内数据共享

java实现线程范围内数据共享：
Thread.crruntThread()
使用HashMap<Thread,Object>

经过A,B,C三个模块都是获得同一个值

public class ThreadDemo20 {
	private static HashMap<Thread,Integer> data=new HashMap<Thread,Integer>();

	static class A{
		public void getData(){
			Thread t=Thread.currentThread();
			int value=data.get(t);
			System.out.println(t.getName()+" from A getData "+value);
		}
	}
	static class B{
		public void getData(){
			Thread t=Thread.currentThread();
			int value=data.get(t);
			System.out.println(t.getName()+" from B getData "+value);
		}
	}
	static class C{
		public void getData(){
			Thread t=Thread.currentThread();
			int value=data.get(t);
			System.out.println(t.getName()+" from C getData "+value);
		}
	}
	
	public static void main(String[] args) {
		for (int i = 0; i < 2; i++) {
			new Thread(new Runnable() {
				@Override
				public void run() {
					int value=new Random().nextInt(1000);
					data.put(Thread.currentThread(), value);
					A a1=new A();
					a1.getData();
					B b1=new B();
					b1.getData();
					C c1=new C();
					c1.getData();
				}
			}).start();;
		}
	}
}

执行结果

Thread-1 from A getData 521
Thread-1 from B getData 521
Thread-1 from C getData 521
Thread-0 from A getData 925
Thread-0 from B getData 925
Thread-0 from C getData 925

java中提供了Threadlocal类已经实现了该
Threadlocal<Integer> tl=new Threadlocal<Integer>()
t1.get();
使得该类在创建对象时候直接就是同一个线程同一个对象 对象不同线程不同，就像你登录后获得你的当前登录的用户时候不会获得别人的用户
来点实际的：

public class UserService {

	private static ThreadLocal<UserService> tl = new ThreadLocal<UserService>();

	private UserService() {}

	public static UserService getInstance() {
		UserService us = tl.get();
		if (us == null) {
			us = new UserService();
			tl.set(us);
		}
		return us;
	}

}

这个大家应该再熟悉不过了。我们使用多个线程来测试一下

public class UserServiceTest {

	public static void main(String[] args) {
		for (int i = 0; i < 4; i++) {
			new Thread(new Runnable() {
				@Override
				public void run() {
					A a=new A();
					a.print();
					B b=new B();
					b.print();
				}
			}).start();
		}
	}

	static class A {
		public void print() {
			UserService us = UserService.getInstance();
			System.out.println("from A "+Thread.currentThread().getName() + "..." + us);
		}
	}

	static class B {
		public void print() {
			UserService us = UserService.getInstance();
			System.out.println("from B "+Thread.currentThread().getName() + "..." + us);
		}
	}
}

测试结果是:同一个线程的UserService是相同的，不论是在A或者B中都能够获得

from A Thread-3...thread.UserService@787d6a
from A Thread-0...thread.UserService@1f4cbee
from A Thread-1...thread.UserService@1f4cbee
from A Thread-2...thread.UserService@787d6a
from B Thread-2...thread.UserService@787d6a
from B Thread-3...thread.UserService@787d6a
from B Thread-0...thread.UserService@1f4cbee
from B Thread-1...thread.UserService@1f4cbee