Java里面进行多线程通信的主要方式就是共享内存的方式,共享内存主要的关注点有两个:可见性和有序性原子性。
Java 内存模型(JMM)解决了可见性和有序性的问题,而锁解决了原子性的问题,理想情况下我们希望做到“同步”和“互斥”。
有以下常规实现方法:
一、数据抽象成一个类,对数据操作的方法封装在类里
public class MyData1 {
private int j = 0;
public static void main(String[] args) {
MyData1 data = new MyData1();
AddRunnable addRunnable = new AddRunnable(data);
DecRunnable decRunnable = new DecRunnable(data);
new Thread(addRunnable).start();
new Thread(decRunnable).start();
}
public synchronized void add() {
j++;
System.out.println("线程:" + Thread.currentThread().getName() + " j为:" + j);
}
public synchronized void dec() {
j--;
System.out.println("线程:" + Thread.currentThread().getName() + " j为:" + j);
}
public int getData() {
return j;
}
}
class AddRunnable implements Runnable {
MyData1 data1 = new MyData1();
public AddRunnable(MyData1 data1) {
this.data1 = data1;
}
@Override
public void run() {
data1.add();
}
}
class DecRunnable implements Runnable {
MyData1 data1 = new MyData1();
public DecRunnable(MyData1 data1) {
this.data1 = data1;
}
@Override
public void run() {
data1.dec();
}
}
二、Runnable对象作为一个类的内部类,共享数据作为这个类的内部变量,每个线程对类的操作封装在外部类中,从而实现各个数据之间的互斥和同步,内部类的各个Runnable对象都可以调用外部方法
public class MyData2 {
private int j = 0;
public synchronized void add() {
j++;
System.out.println("线程:" + Thread.currentThread().getName() + " j为:" + j);
}
public synchronized void dec() {
j--;
System.out.println("线程:" + Thread.currentThread().getName() + " j为:" + j);
}
public int getData() {
return j;
}
}
class TestThread {
public static void main(String[] args) {
final MyData2 data = new MyData2();
for (int i = 0; i < 2; i++) {
new Thread(new Runnable() {
@Override
public void run() {
data.add();
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
data.dec();
}
}).start();
}
}
}