题目描述

 

解析：

class Foo {public int a = 0;public Foo() {}public void first(Runnable printFirst) throws InterruptedException {// printFirst.run() outputs "first". Do not change or remove this line.printFirst.run();a++;}public void second(Runnable printSecond) throws InterruptedException {while(true){if(a == 1){printSecond.run();a++;break;}else{Thread.yield();}}// printSecond.run() outputs "second". Do not change or remove this line.}public void third(Runnable printThird) throws InterruptedException {while(true){if(a == 2){printThird.run();break;}else{Thread.yield();}}// printThird.run() outputs "third". Do not change or remove this line.}
}