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threadlocal实例及原理     所属分类 java 浏览量 38
ThreadLocal
线程局部变量  线程本地变量
每一个线程都有一份变量的副本 互相不影响 空间换时间 



public class ThreadLocalDemo {

	static ThreadLocal<Integer> threadLocalSeq = new ThreadLocal<Integer>() {
		@Override
		protected Integer initialValue() {
			return 0;
		}
	};

	public static void main(String[] args) throws Exception {

		for (int i = 0; i < 3; i++) {
			MyThread t = new MyThread();
			t.setName("mythread" + i);
			t.start();
		}
	}

	private static class MyThread extends Thread {
		public void run() {
			for (int i = 0; i < 3; i++) {
				try {
					Thread.sleep(1000);
				} catch (Exception e) {
					System.out.println("sleep error," + e);
				}
				int seq = threadLocalSeq.get();
				System.out.println(Thread.currentThread().getName() + ":" + seq);
				threadLocalSeq.set(seq + 1);
			}
			System.out.println(Thread.currentThread().getName()+" done!");
		}
	}
}



ThreadLocal实现原理 public void set(T value) { Thread t = Thread.currentThread(); // 获取线程的ThreadLocalMap ThreadLocalMap map = getMap(t); if (map != null) map.set(this, value); else // map为空,创建 createMap(t, value); } ThreadLocalMap getMap(Thread t) { return t.threadLocals; } void createMap(Thread t, T firstValue) { t.threadLocals = new ThreadLocalMap(this, firstValue); } 完整例子代码 https://gitee.com/dyyx/hellocode/blob/master/src/dyyx/conc/ThreadLocalDemo.java

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