13.java死锁举例 生产消费者模式
*同步一般都是外层是while循环，里面是同步代码块，再里面是循环
*不安全与死锁都因为在判断中出错
死锁举例：
package com.qianfeng.demo02;
class DeadLockThread implements Runnable {
private static String milk = "牛奶";
private static String bread = "面包";
boolean flag = true;
public void run() {
if (flag) {
synchronized (bread) {
System.out.println(Thread.currentThread().getName() + "\t已经拥有了"
+ bread + "，还要：" + milk);
synchronized (milk) {
System.out.println(Thread.currentThread().getName() + "既有"
+ bread + ",又有：" + milk);
}
}
} else {
synchronized (milk) {
System.out.println(Thread.currentThread().getName() + "\t已经拥有了"
+ milk + "，还要：" + bread);
synchronized (bread) {
System.out.println(Thread.currentThread().getName() + "既有"
+ milk + ",又有：" + bread);
}
}
}
}
}
public class Demo_DeadLock {
public static void main(String[] args) {
DeadLockThread dt1 = new DeadLockThread();
DeadLockThread dt2 = new DeadLockThread();
dt1.flag = true;
dt2.flag = false;
Thread t1 = new Thread(dt1, "张三");
Thread t2 = new Thread(dt2, "李四");
t1.start();
t2.start();
}
}
生产者消费者模式
*建两个同步方法，一个消费，一个生产，用while循环判断条件，在里面加上wait和notify
package com.qianfeng.demo03;
class Egg {
private int id;
public Egg(int id) {
this.id = id;
}
public String toString() {
return "鸡蛋：" + id;
}
}
class Basket {
private Egg[] eggs = new Egg[8];// 装鸡蛋的数组
private int index = 0;// 控制数组的下标
public synchronized void addEgg(Egg egg) {
while (index == 8) {
try {
System.out.println(Thread.currentThread().getName()
+ "\t容器满了，母鸡处于等待。。");
wait();// 生产者处于等待，释放锁资源。。。
} catch (InterruptedException e) {
e.printStackTrace();
}
}
eggs[index] = egg;// 存入鸡蛋//index:0-7
System.out.println("\t\t生产者生产鸡蛋：" + egg);
try {
Thread.sleep((int) (Math.random() * 1000));
} catch (InterruptedException e) {
e.printStackTrace();
}
index++;// 下标向上走一个//index:1-8
notify();// 唤醒吃货,存在空唤醒
}
public synchronized void getEgg() {
while (index == 0) {
try {
System.out.println(Thread.currentThread().getName()
+ "\t容器空了，吃货等待。。");
wait();// 消费者线程处于等待。。放弃cpu的资源，同时也释放了锁
} catch (InterruptedException e) {
e.printStackTrace();
}
}
index--;// 下标向下减1，取鸡蛋
try {
Thread.sleep((int) (Math.random() * 1000));
} catch (InterruptedException e) {
e.printStackTrace();
}
Egg egg = eggs[index];
System.out.println("消费者吃鸡蛋：" + egg);
notify();// 唤醒母鸡，空唤醒
}
}
class Producer implements Runnable {
private int id = 1;
private Basket basket;
public Producer(Basket basket) {
this.basket = basket;
}
public void run() {
while (true) {
Egg egg = new Egg(id++);
basket.addEgg(egg);
}
}
}
class Customer implements Runnable {
private Basket basket;
public Customer(Basket basket) {
this.basket = basket;
}
public void run() {
// 循环消费鸡蛋：
while (true) {
basket.getEgg();
}
}
}
public class TestProAndCus {
public static void main(String[] args) {
Basket basket = new Basket();
Producer p1 = new Producer(basket);
Customer c1 = new Customer(basket);
Thread t1 = new Thread(p1, "母鸡");
Thread t2 = new Thread(c1, "吃货");
t1.start();
t2.start();
}
}
例子二
package com.qianfeng.homework;
import java.util.ArrayList;
import java.util.List;
class JianEgg {
private int id;
static boolean flag = true;//
public JianEgg(int id) {
super();
this.id = id;
}
public String toString() {
return "煎鸡蛋" + id;
}
}
class Procuder1 implements Runnable {
private List<JianEgg> plant;
private int id = 1;
public Procuder1(List<JianEgg> plant) {
super();
this.plant = plant;
}
public void run() {
while (true) {
synchronized (plant) {
JianEgg je = new JianEgg(id++);
while (!JianEgg.flag) {// F：容器是满了，应该消费
try {
System.out.println(Thread.currentThread().getName()
+ "\t等待。。");
plant.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("生产者生产鸡蛋：" + je);
plant.add(je);
plant.notify();
JianEgg.flag = false;// 生产后容器满了，改为false，下次就消费
}
}
}
}
class Customer1 implements Runnable {
private List<JianEgg> plant;
public Customer1(List<JianEgg> plant) {
super();
this.plant = plant;
}
public void run() {
while (true) {
synchronized (plant) {
while (JianEgg.flag) {// T：容器是空的，应该生产
try {
System.out.println("\t"
+ Thread.currentThread().getName() + "\t等待。。");
plant.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
JianEgg je = plant.get(0);
plant.remove(0);
System.out.println("\t\t消费者吃鸡蛋：" + je);
plant.notify();
JianEgg.flag = true;// 吃完，容器就空了，改为T，下次该生产了
}
}
}
}
public class HomeWork03 {
public static void main(String[] args) {
List<JianEgg> list = new ArrayList<>();
Procuder1 p1 = new Procuder1(list);
Customer1 c1 = new Customer1(list);
Thread t1 = new Thread(p1, "老公");
Thread t2 = new Thread(c1, "媳妇");
t1.start();
t2.start();
}
}
