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一、普通的int型自增长测试
package AtomicInteger;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * @author xiaobu * @version JDK1.8.0_171 * @date on 2018/8/7 16:15 */public class IntValueIncrementTest { public static void main(String[] args) throws InterruptedException { intValueIncrement(); Thread.sleep(5000); //39991 <40000 System.out.println("最终的结果："+value); } private static int value=0; public static synchronized void intValueIncrement(){ ExecutorService service = Executors.newFixedThreadPool(10000); for(int i=0;i<10000;i++){ service.execute(()->{ for(int j=0;j<4;j++){ System.out.println(value++); } }); } }} 二、用volatile修饰的int自增长类型。
package AtomicInteger;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * @author xiaobu * @version JDK1.8.0_171 * @date on 2018/8/7 16:15 */public class IntVolatileValueIncrementTest { public static void main(String[] args) throws InterruptedException { intValueIncrement(); Thread.sleep(5000); // 39993 <4000 System.out.println("最终的结果：" + value); } private static volatile int value = 0; public static synchronized void intValueIncrement() { ExecutorService service = Executors.newFixedThreadPool(10000); for (int i = 0; i < 10000; i++) { service.execute(() -> { for (int j = 0; j < 4; j++) { System.out.println(value++); } }); } }} 三、AtomicInteger原子操作类类型
package AtomicInteger;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.atomic.AtomicInteger;/** * @author xiaobu * @version JDK1.8.0_171 * @date on 2018/8/7 16:08 */public class AtomicIntegerTest { public static final AtomicInteger atomicInteger = new AtomicInteger(0); public static void main(String[] args) throws InterruptedException { atomicIntegerTest(); Thread.sleep(3000); //40000 System.out.println("最终结果是" + atomicInteger.get()); } private static void atomicIntegerTest() { ExecutorService executorService = Executors.newFixedThreadPool(10000); for (int i = 0; i < 10000; i++) { executorService.execute(() -> { for (int j = 0; j < 4; j++) { System.out.println(atomicInteger.getAndIncrement()); } }); } executorService.shutdown(); }} volatile的作用：
1.保证此变量对所有的线程的可见性
2.禁止指令重排序优化。结果表明还是会存在并发的问题。因为java的运算（自增）不是原子性的。
CAS(Compare And Swap 比较并交换 ) 的并发算法称为 无锁定算法所以不阻塞。
可以避免多线程的优先级倒置和死锁情况的发生，提升在高并发处理下的性能。
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