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Java synchronized 作用于普通方法、静态方法、方法块
package chapter3;
/**
* @program: studythread2
* @description: synchronized Demo
* @author: diaolizhi
* @create: 2018-11-13 10:29
**/
public class SynchronizedDemo {
/**
* @Description: 作用在普通方法上面的 synchronized
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
public synchronized void out() throws InterruptedException {
System.out.println(Thread.currentThread().getName());
Thread.sleep(5000);
System.out.println(Thread.currentThread().getName() + "结束。");
}
/**
* @Description: 使用 synchronized 修饰静态方法
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
public static synchronized void staticOut() throws InterruptedException {
System.out.println(Thread.currentThread().getName());
Thread.sleep(5000);
System.out.println(Thread.currentThread().getName() + "结束。");
}
private Object object = new Object();
/**
* @Description: 使用 synchronized 修饰代码块,锁住一个对象
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
public void myOut() throws InterruptedException {
System.out.println(Thread.currentThread().getName() + "进入 myOut 方法");
synchronized (object) {
System.out.println(Thread.currentThread().getName() + "进入同步代码块");
Thread.sleep(5000);
System.out.println(Thread.currentThread().getName() + "退出同步代码块");
}
System.out.println(Thread.currentThread().getName() + "退出 myOut 方法");
}
public static void main(String[] args) {
}
}
package chapter3_test;
import chapter3.SynchronizedDemo;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
/**
* @program: studythread2
* @description:
* @author: diaolizhi
* @create: 2018-11-13 10:34
**/
public class SynchronizedTest {
/**
* @Description: 用 synchronized 修饰一个普通方法。创建两个线程分别调用 SynchronizedDemo 的 out 方法,发现它们互不干扰。
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
@Test
void testLockCommonMethodAndTwoObj() throws InterruptedException {
SynchronizedDemo synchronizedDemo = new SynchronizedDemo();
SynchronizedDemo synchronizedDemo1 = new SynchronizedDemo();
new Thread(() -> {
try {
synchronizedDemo.out();
} catch (InterruptedException e) {
e.printStackTrace();
}
}).start();
new Thread(() -> {
try {
synchronizedDemo1.out();
} catch (InterruptedException e) {
e.printStackTrace();
}
}).start();
Thread.sleep(20000);
}
/**
* @Description: 锁住普通方法,创建两个线程调用同一个对象的 out 方法,发现只有当一个线程释放锁的时候,另一个线程才能访问。
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
@Test
void testLockCommonMethodAndOneObj() throws InterruptedException {
SynchronizedDemo synchronizedDemo = new SynchronizedDemo();
Runnable runnable = new Runnable() {
@Override
public void run() {
try {
synchronizedDemo.out();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
new Thread(runnable).start();
new Thread(runnable).start();
Thread.sleep(20000);
}
/**
* @Description: 对于普通方法,两个线程互不影响,但是对于静态方法,两个不同的对象在某一时刻,只有一个能访问。
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
@Test
@DisplayName("两个线程调用两个对象的静态方法")
void lockStaticMethodAndTwoObj() throws InterruptedException {
SynchronizedDemo synchronizedDemo = new SynchronizedDemo();
SynchronizedDemo synchronizedDemo1 = new SynchronizedDemo();
new Thread(() -> {
try {
synchronizedDemo.staticOut();
} catch (InterruptedException e) {
e.printStackTrace();
}
}).start();
new Thread(() -> {
try {
synchronizedDemo1.staticOut();
} catch (InterruptedException e) {
e.printStackTrace();
}
}).start();
Thread.sleep(20000);
}
/**
* @Description: 在普通方法中使用 synchronized 锁住一个对象,发现在多线程中只有一个线程可以进入该同步代码块。
* (因为必须锁住同一个对象,所以测试方法中只创建了一个对象。)
* @Param: []
* @return: void
* @Author: diaolizhi
* @Date: 2018/11/13
*/
@Test
@DisplayName("两个线程访问同一个对象的同步代码块")
void testLockBlockAndOneObj() throws InterruptedException {
SynchronizedDemo synchronizedDemo = new SynchronizedDemo();
Runnable runnable = () -> {
try {
synchronizedDemo.myOut();
} catch (InterruptedException e) {
e.printStackTrace();
}
};
new Thread(runnable).start();
new Thread(runnable).start();
Thread.sleep(20000);
}
}
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