ResortSeqDemo.java

package com.xd.thread;public class ResortSeqDemo {volatile int a=0;boolean flag=false;/*多线程下flag=true可能先执行，还没走到a=1就被挂起其他线程进入method02的判断，修改a的值=5，而不是6*/public void method01(){a=1;flag=true;}public void method02(){if (flag){a+=5;System.out.println("******最终值a："+a);}}public static void main(String[] args) {ResortSeqDemo resortSeq = new ResortSeqDemo();new Thread(()->{resortSeq.method01();},"ThreadA").start();new Thread(()->{resortSeq.method02();},"ThreadB").start();}}

SingletonDemo.java

package com.xd.thread;/*** 单例模式 DCL 双端检查锁* 当前类的对象必须本类创建，构造方法私有，本类中对外一个公共可以访问的方法返回该对象*/class Singleton1{private static Singleton1 instance = null;private Singleton1() {System.out.println(Thread.currentThread().getName() + "\t Singleton1构造方法执行了");}public static Singleton1 getInstance(){if (instance == null) {instance = new Singleton1();}return instance;}}public class SingletonDemo {public static void main(String[] args) {//main线程操作
//        System.out.println(Singleton.getInstance() == Singleton.getInstance());
//        System.out.println(Singleton.getInstance() == Singleton.getInstance());
//        System.out.println(Singleton.getInstance() == Singleton.getInstance());for (int i = 0; i < 10; i++) {new Thread(()->{Singleton1.getInstance();},String.valueOf(i)).start();}}}

SingletonDemo2.java

package com.xd.thread;/*** 单例模式 DCL 双端检查锁* 当前类的对象必须本类创建，构造方法私有，本类中对外一个公共可以访问的方法返回该对象*/class Singleton2{private volatile static Singleton2 instance = null;private Singleton2() {System.out.println(Thread.currentThread().getName() + "\t Singleton2构造方法执行了");}public static Singleton2 getInstance(){if(instance == null){synchronized (Singleton2.class){if (instance == null) {instance = new Singleton2();}}}return instance;}}public class SingletonDemo2 {public static void main(String[] args) {//main线程操作
//        System.out.println(Singleton.getInstance() == Singleton.getInstance());
//        System.out.println(Singleton.getInstance() == Singleton.getInstance());
//        System.out.println(Singleton.getInstance() == Singleton.getInstance());for (int i = 0; i < 10; i++) {new Thread(()->{Singleton2.getInstance();},String.valueOf(i)).start();}}}

VolatileDemo.java

package com.xd.thread;import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;class MyData {volatile int number = 0;//volatile int number = 0;AtomicInteger atomicInteger = new AtomicInteger();public void setNumber(){this.number = 60;}public void  addPlusPlus(){number++;}public void atomicPlusPlis(){atomicInteger.getAndIncrement();//i++}}public class VolatileDemo {public static void main(String[] args) {/*** 创建20个线程，每个线程执行1000次 number++操作，最后打印 number的结果值*/System.out.println("原子性操作...");MyData myData = new MyData();//创建20个线程，每个线程执行1000次for (int i = 1; i <= 20; i++) {new Thread(()->{for (int j = 0; j < 1000; j++) {myData.addPlusPlus();myData.atomicPlusPlis();}}, String.valueOf(i)).start();}//20个线程都执行完毕后，打印number值while (Thread.activeCount() > 2){ // mian,gcThread.yield();}System.out.println(Thread.currentThread().getName()+"\t int类型的最终的number值====" + myData.number);System.out.println(Thread.currentThread().getName()+"\t atomicInteger类型的最终的number值====" + myData.atomicInteger);}/*** 可见性演示*/private static void method01() {System.out.println("可见性的演示。。。");MyData myData = new MyData();// 新创建的线程new Thread(()->{System.out.println(Thread.currentThread().getName()+"\t 执行。。。");try {TimeUnit.SECONDS.sleep(3);} catch (InterruptedException e) {e.printStackTrace();}myData.setNumber();},"ThreadA").start();// main线程while (myData.number == 0){//main线程 访问的number变量，一直为0System.out.println("main。。。");}System.out.println(Thread.currentThread().getName()+"\t main线程获取到了"+ myData.number);}}