1，
2，
3，
4，相关例题
Answer-1：
解决办法：
注意这里使用lock-synchronized同步以及屏障
package com.cnblogs.mufasa.demo1.Answer1114;
class Foo {
private boolean firstBlock;
private boolean secondBlock;
private Object lock=new Object();
public Foo() {
}
public void first(Runnable printFirst) throws InterruptedException {
synchronized(lock){
// printFirst.run() outputs "first". Do not change or remove this line.
printFirst.run();
firstBlock=true;
lock.notifyAll();
}
}
public void second(Runnable printSecond) throws InterruptedException {
synchronized(lock){
while(!firstBlock){
lock.wait();
}
// printSecond.run() outputs "second". Do not change or remove this line.
printSecond.run();
secondBlock=true;
lock.notifyAll();
}
}
public void third(Runnable printThird) throws InterruptedException {
synchronized(lock){
while(!secondBlock){
lock.wait();
}
// printThird.run() outputs "third". Do not change or remove this line.
printThird.run();
}
}
}
Answer-2:
解决方法：
①定义一个布尔标识符flag,决定轮替输出；
②设置一个lock-synchronized同步；
package com.cnblogs.mufasa.demo1.Answer1115;
class FooBar {
private int n;
private boolean flag=false;//定义一个布尔标识位
private Object lock=new Object();//同步锁
public FooBar(int n) {
this.n = n;
}
public void foo(Runnable printFoo) throws InterruptedException {
for (int i = 0; i < n; i++) {
synchronized (lock){
while (flag){
lock.wait();
}
// printFoo.run() outputs "foo". Do not change or remove this line.
printFoo.run();
flag=true;
lock.notifyAll();
}
}
}
public void bar(Runnable printBar) throws InterruptedException {
for (int i = 0; i < n; i++) {
synchronized (lock) {
while (!flag) {
lock.wait();
}
// printBar.run() outputs "bar". Do not change or remove this line.
printBar.run();
flag=false;
lock.notifyAll();
}
}
}
}