java 共享资源

防止任务在共享资源上产生冲突除了加锁的第二种方式是 根除对变量的共享。线程本地存储是一种自动化机制，可以为使用相同变量的每个不同线程都创建不懂的存储。

public class ThreadLocalVariableHolder {
	private static ThreadLocal<Integer> value = new ThreadLocal<Integer>() {
		private Random rand = new Random(47);

		protected synchronized Integer initialValue() {
			return rand.nextInt(10000);
		}
	};

	public static void increment() {
		value.set(value.get() + 1);
	}

	public static int get() {
		return value.get();
	}

	public static void main(String[] args) throws Exception {
		ExecutorService exec = Executors.newCachedThreadPool();
		for (int i = 0; i < 5; i++) {
			exec.execute(new Accessor(i));
		}
		TimeUnit.SECONDS.sleep(1);
		exec.shutdownNow();
	}
}

class Accessor implements Runnable {
	private final int id;

	public Accessor(int idn) {
		this.id = idn;
	}

	public void run() {
		while (!Thread.currentThread().isInterrupted()) {
			ThreadLocalVariableHolder.increment();
			System.out.println(this);
			Thread.yield();
		}
	}

	public String toString() {
		return "#" + id + ":" + ThreadLocalVariableHolder.get();
	}
}