生产者与消费者
面试的：单例模式、排序问题、生产者消费者、死锁（需要会手写）
1、synchronzied 版的
package com.zkw.JUC并发编程;
/**
* 线程通信，生产者与消费者问题： 等待唤醒，通知唤醒
* 线程交替进行 A B同时操作一变量 num = 0；
* A num+1
* B num-1
*/
public class PC {
public static void main(String[] args) {
Data data = new Data();
new Thread(()->{
for (int i = 0; i < 10; i++) {
try {
data.increment();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
},"A").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
try {
data.decrement();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
},"B").start();
}
}
//判断等待，业务，通知
class Data{
// 资源类
private int num = 0;
// +1
public synchronized void increment() throws InterruptedException {
if (num!=0){
this.wait();
}
num++;
System.out.println(Thread.currentThread().getName()+":"+num);
this.notifyAll();
}
// -1
public synchronized void decrement() throws InterruptedException {
if (num==0){
this.wait();
}
num--;
System.out.println(Thread.currentThread().getName()+":"+num);
this.notifyAll();
}
}
问题存在，当存在A、B、C、D就会出现问题，的解决方案
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把 if 改成 while 防止虚假唤醒
package com.zkw.JUC并发编程;
/**
* 线程通信，生产者与消费者问题： 等待唤醒，通知唤醒
* 线程交替进行 A B同时操作一变量 num = 0；
* A num+1
* B num-1
*/
public class PC {
public static void main(String[] args) {
Data data = new Data();
new Thread(()->{
for (int i = 0; i < 10; i++) {
try {
data.increment();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
},"A").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
try {
data.decrement();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
},"B").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
try {
data.increment();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
},"C").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
try {
data.decrement();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
},"D").start();
}
}
//判断等待，业务，通知
class Data{
// 资源类
private int num = 0;
// +1
public synchronized void increment() throws InterruptedException {
while (num!=0){
this.wait();
}
num++;
System.out.println(Thread.currentThread().getName()+":"+num);
this.notifyAll();
}
// -1
public synchronized void decrement() throws InterruptedException {
while (num==0){
this.wait();
}
num--;
System.out.println(Thread.currentThread().getName()+":"+num);
this.notifyAll();
}
}
2、JUC版的生产者与消费者
package com.zkw.JUC并发编程;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class PC2 {
public static void main(String[] args) {
Data2 data2 = new Data2();
new Thread(()->{
for (int i = 0; i < 5; i++) {
data2.increment();
}
},"A").start();
new Thread(()->{
for (int i = 0; i < 5; i++) {
data2.decrement();
}
},"B").start();
new Thread(()->{
for (int i = 0; i < 5; i++) {
data2.increment();
}
},"C").start();
new Thread(()->{
for (int i = 0; i < 5; i++) {
data2.decrement();
}
},"D").start();
}
}
//判断等待，业务，通知
class Data2{
// 资源类
private int num = 0;
Lock lock = new ReentrantLock();
Condition condition = lock.newCondition();
// +1
public void increment() {
lock.lock();
try {
while (num!=0){
condition.await();//线程等待
}
num++;
condition.signalAll();//唤醒所有等待的线程
System.out.println(Thread.currentThread().getName()+":"+num);
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();//解锁
}
}
// -1
public void decrement() {
lock.lock();
try {
while (num==0){
condition.await();
}
num--;
condition.signalAll();
System.out.println(Thread.currentThread().getName()+":"+num);
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
3、condition能做到精准通知
package com.zkw.JUC并发编程;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 让A、B、C按顺序执行
*/
public class C {
public static void main(String[] args) {
Data3 data3 = new Data3();
new Thread(()->{
for (int i = 0; i < 10; i++) {
data3.printA();
}
},"A").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
data3.printB();
}
},"B").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
data3.printC();
}
},"C").start();
}
}
class Data3{
//资源类
Lock lock = new ReentrantLock();
Condition condition1 = lock.newCondition();
Condition condition2 = lock.newCondition();
Condition condition3 = lock.newCondition();
private int number = 1;// 1A 2B 3C
public void printA(){
lock.lock();
try {
//业务，判断 -> 执行 -> 通知
while (number!=1){
//等待
condition1.await();
}
System.out.println(Thread.currentThread().getName()+"=>AAAAAA");
//唤醒，唤醒指定的线程 B
number = 2;
condition2.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void printB(){
lock.lock();
try {
//业务，判断 -> 执行 -> 通知
while (number!=2){
//等待
condition2.await();
}
System.out.println(Thread.currentThread().getName()+"=>BBBBBBB");
//唤醒，唤醒指定的线程 C
number = 3;
condition3.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void printC(){
lock.lock();
try {
//业务，判断 -> 执行 -> 通知
while (number!=3){
//等待
condition3.await();
}
System.out.println(Thread.currentThread().getName()+"=>CCCCCCCCC");
//唤醒，唤醒指定的线程 A
number = 1;
condition1.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}