java中线程sleep和加锁synchronized 关键字的一些区别

第一种代码：没有synchronized 

public class ThreadTest1Test { //main函数public static void main(String[] args) {ThreadTest2 r = new ThreadTest2();Thread t1 = new Thread(r);Thread t2 = new Thread(r);t1.start();t2.start();}}//线程函数 public class ThreadTest2 implements Runnable {private static int temp = 0;public void run() {this.add();}public void add() {temp++;try {Thread.sleep(10);} catch (InterruptedException e) {}System.out.println(Thread.currentThread().getName() + " " + temp);}}//此时输出的结果是//Thread-1 2//Thread-0 2

加上synchronized 

 public class ThreadTest1Test { //main方法public static void main(String[] args) {ThreadTest2 r = new ThreadTest2();Thread t1 = new Thread(r);Thread t2 = new Thread(r);t1.start();t2.start();}}public class ThreadTest2 implements Runnable {//线程函数private static int temp = 0;public void run() {this.add();}public synchronized void add() {temp++;try {Thread.sleep(10);} catch (InterruptedException e) {}System.out.println(Thread.currentThread().getName() + " " + temp);}}//结果为//Thread-1 1//Thread-0 2

 

第二种

public class ThreadTest1Test { //main方法public static void main(String[] args) {Thread t1 = new Thread(new ThreadTest2()); Thread t2 = new Thread(new ThreadTest2());t1.start();t2.start();}}public class ThreadTest2 implements Runnable {//线程函数private static int temp = 0;public void run() {this.add();}public synchronized void add() {temp++;try {Thread.sleep(10);} catch (InterruptedException e) {}System.out.println(Thread.currentThread().getName() + " " + temp);}}//输出的结果//Thread-0 2//Thread-1 2

 

 

 

注意比较第一种和第二种输出结果上的区别

 

特别是第二种 在创建线程类的时候是创建两个线程

 

而第一种  在创建线程类的时候创建一个