原理 https://blog.csdn.net/a837199685/article/details/52712547

例子https://www.cnblogs.com/sweetchildomine/p/8807059.html

public class Test {

    static ExecutorService executorService = Executors.newFixedThreadPool(1);

    public static void main(String[] args) {
        //子執行緒每次new 所以會複製執行緒的InheritableThreadLocal,結果正確
 
//        withoutThreadPool(10);//true
        //因執行緒池複用執行緒,不會每次new 所以不會更新父執行緒InheritableThreadLocal 的值,導致結果錯誤
        withThreadPool(10);//true or false
    }

    public static void withoutThreadPool(int c){
        for(int i=0;i<c;i++){
            Integer var1 = (int)(Math.random()*100);
            Integer var2 = (int
 
)(Math.random()*100);
            MyContextHolder.set(var1);
            threadRun(var1,var2);
        }
    }

    public static void withThreadPool(int c){
        for(int i=0;i<c;i++){
            Integer var1 = (int)(Math.random()*100);
            Integer var2 = (int)(Math.random()*100);
            
 
MyContextHolder.set(var1);
            threadPoolExecute(var1,var2);
        }
    }

    public static void threadRun(Integer var1,Integer var2){
        new Thread(()->assert1(var1,var2)).start();
    }

    public static void threadPoolExecute(Integer var1,Integer var2){
//        executorService.execute(()->assert1(var1,var2));
        executorService.execute(TtlRunnable.get(()->assert1(var1,var2)) );
    }


    public static void assert1(Integer var1,Integer var2){
        System.out.println(MyContextHolder.get()*var2==var1*var2);
    }


    public static class MyContextHolder{

//        private static ThreadLocal<Integer> stringThreadLocal = new InheritableThreadLocal<>();
        private static ThreadLocal<Integer> stringThreadLocal = new TransmittableThreadLocal<>();

        public static void set(Integer data) {
            stringThreadLocal.set(data);
        }

        public static Integer get() {
            return stringThreadLocal.get();
        }
    }

}