并发编程 - ThreadLocal 用法

ThreadLocal 类： 用来提供线程内部的局部变量。 这种变量在线程的生命周期内起作用，减少同一个线程内多个函数或者组件之间一些公共变量的传递的复杂度

• ThreadLocal实例通常来说都是private static类型的, 用于关联线程和线程的上下文

• ThreadLocal设计的初衷: 提供线程内部的局部变量, 在本线程内随时随地可取, 隔离其他线程

public class AnswerApp {

    private static ThreadLocal<Integer> value = ThreadLocal.withInitial(() -> 0);

    public static void main(String[] args) {

        ExecutorService executors = Executors.newCachedThreadPool();

        for (int i = 1; i <= 5; i++) {
            executors.execute(new MyRunnable(i));

            // 线程 main 的累加值
            value.set(value.get() + i);
        }

        System.out.println(Thread.currentThread().getName() + "'s summation value: " + value.get());
    }


    static class MyRunnable implements Runnable {
        private int index;

        MyRunnable(int index) {
            this.index = index;
        }

        @Override
        public void run() {
            System.out.println("thread " + index + "'s init value: " + value.get());

            for (int i = 0; i < 10; i++) {
                value.set(value.get() + i);
            }

            System.out.println("thread " + index + "'s summation value: " + value.get());
        }
    }

}

thread 1's init value: 0
thread 3's init value: 0
main's summation value: 15
thread 2's init value: 0
thread 5's init value: 0
thread 3's summation value: 45
thread 1's summation value: 45
thread 4's init value: 0
thread 5's summation value: 45
thread 2's summation value: 45
thread 4's summation value: 45

Reference

• ThreadLocal和synchronized的区别

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来源： https://blog.csdn.net/u010979642/article/details/90673010