1.生产者和消费者问题Synchronized版
面试:单例模式、排序算法、生产者消费者、死锁
package com.kuang.pc;
/**
* 线程之间的通信问题,生产者和消费者问题! 等待唤醒 ,通知唤醒
* 线程交替执行 A B 操作同一个变量 num=0
* A num+1;
* B num-1;
*/
public class A {
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{//数字 资源类
private int num = 0;
//+1
public synchronized void increment() throws InterruptedException {
if(num!=0){
//等待
this.wait();
}
num++;
//通知其他线程,我+1完毕了
System.out.println(Thread.currentThread().getName()+"=>"+num);
this.notifyAll();
}
//+1
public synchronized void decrement() throws InterruptedException {
if(num==0){
//等待
this.wait();
}
num--;
//通知其他线程,我-1完毕了
System.out.println(Thread.currentThread().getName()+"=>"+num);
this.notifyAll();
}
}
问题A B C D 开四个线程跑,在if判断之后被唤醒,没判断条件被执行了两次增加,导致的虚假唤醒问题。
package com.kuang.pc;
/**
* 线程之间的通信问题,生产者和消费者问题! 等待唤醒 ,通知唤醒
* 线程交替执行 A B 操作同一个变量 num=0
* A num+1;
* B num-1;
*/
public class A {
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{//数字 资源类
private int num = 0;
//+1
public synchronized void increment() throws InterruptedException {
while (num!=0){
//等待
this.wait();
}
num++;
//通知其他线程,我+1完毕了
System.out.println(Thread.currentThread().getName()+"=>"+num);
this.notifyAll();
}
//+1
public synchronized void decrement() throws InterruptedException {
while (num==0){
//等待
this.wait();
}
num--;
//通知其他线程,我-1完毕了
System.out.println(Thread.currentThread().getName()+"=>"+num);
this.notifyAll();
}
}
2.新版Lock锁解决消费者生产者问题。
package com.kuang.pc;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 线程之间的通信问题,生产者和消费者问题! 等待唤醒 ,通知唤醒
* 线程交替执行 A B 操作同一个变量 num=0
* A num+1;
* B num-1;
*/
public class B {
public static void main(String[] args) {
Data1 data = new Data1();
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 Data1 {//数字 资源类
private int num = 0;
Lock lock=new ReentrantLock();
Condition condition = lock.newCondition();
// condition.await();等待
// condition.signalAll();唤醒全部
//+1
public void increment() throws InterruptedException {
lock.lock();
try {
//业务代码
while (num != 0) {
//等待
condition.await();
}
num++;
System.out.println(Thread.currentThread().getName() + "=>" + num);
//通知其他线程,我+1完毕了
condition.signalAll();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
//+1
public void decrement() throws InterruptedException {
lock.lock();
try {
//业务代码
while (num == 0) {
//等待
condition.await();
}
num--;
System.out.println(Thread.currentThread().getName() + "=>" + num);
//通知其他线程,我-1完毕了
condition.signalAll();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
任何一个新的技术,绝对不是仅仅只覆盖了原来的技术,优势,和补充!
Condition 优势精准通知,唤醒线程
文章来源:https://www.toymoban.com/news/detail-731565.html
package com.kuang.pc;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 线程之间的通信问题,生产者和消费者问题! 等待唤醒 ,通知唤醒
* 线程交替执行 A B 操作同一个变量 num=0
* A num+1;
* B num-1;
*/
public class C {
public static void main(String[] args) {
Data2 data = new Data2();
new Thread(()->{
for (int i = 0; i < 10; i++) {
data.printA();
}
},"A").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
data.printB();
}
},"B").start();
new Thread(()->{
for (int i = 0; i < 10; i++) {
data.printC();
}
},"C").start();
}
}
// 判断等待,业务,通知
class Data2 {//数字 资源类
private Lock lock=new ReentrantLock();
private Condition condition1 = lock.newCondition();
private Condition condition2 = lock.newCondition();
private Condition condition3 = lock.newCondition();
private int num=1;
public void printA(){
lock.lock();
try {
if (num!=1){
//等待
condition1.await();
}
num=2;
System.out.println(Thread.currentThread().getName()+":Aaa");
//唤醒,唤醒指定的人,B
condition2.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void printB(){
lock.lock();
try {
if (num!=2){
condition2.await();
}
num=3;
System.out.println(Thread.currentThread().getName()+":Bbb");
condition3.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void printC(){
lock.lock();
try {
if (num!=3){
condition3.await();
}
System.out.println(Thread.currentThread().getName()+":Ccc");
num=1;
condition1.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
精准唤醒线程 Condition文章来源地址https://www.toymoban.com/news/detail-731565.html
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