Java线程同步实例

Java线程同步实例

package lab8.wu;
public class mythread {
public static void main(String[] args) {
new Create("thread1");
new Create("thread2");
}
}
class Create implements Runnable {
static int a = 10;
private Thread t;

public Create(String name) {
t = new Thread(this);
t.setName(name);
t.start();
}

public void run() {
System.out.println("进入同步前"+t.getName()+" "+a);
synchronized (this) {
Thread t = Thread.currentThread();
for (int i = 0; i < 3; i++) {
a++;
System.out.println(t.getName() + "  " + i+"  a="+a);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
}
}
}
}

运行结果，thread1和thread2是乱序的，synchronized并未起到作用，synchronized锁住的是两个对象，彼此之间不造成影响：



对比代码：

package lab8.wu;

public class mythread2 {
public static void main(String[] args) {
Create2 create2=new Create2("th");
Thread th1=new Thread(create2,"thread1");
Thread th2=new Thread(create2,"thread2");
th1.start();
th2.start();
}
}

class Create2 implements Runnable {
static int a = 10;
private Thread t;

public Create2(String name) {
t = new Thread(this);
t.setName(name);
t.start();
}

public void run() {
Thread t = Thread.currentThread();
System.out.println("进入同步前"+t.getName()+" "+a);
synchronized (this) {
for (int i = 0; i < 3; i++) {
a++;
System.out.println(t.getName() + "  " + i+"  a="+a);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
}
}
}
}

运行结果，synchronized起到作用，在synchronized中的代码同一时间不能被不同的线程同时进入：