多线程设计模式 －－ futrue
2009-09-17 00:00:00 来源：WEB开发网数据接口
Java代码
public interface Data {
public abstract String getContent();
}
真正需要的数据对象
Java代码
public class RealData implements Data {
private final String content;
public RealData(int count, char c) {
System.out.println(" making RealData(" + count + ", " + c + ") BEGIN");
char[] buffer = new char[count];
for (int i = 0; i < count; i++) {
buffer[i] = c;
try {
Thread.sleep(100);
} catch (InterruptedException e) {
}
}
System.out.println(" making RealData(" + count + ", " + c + ") END");
this.content = new String(buffer);
}
public String getContent() {
return content;
}
}
//异步数据
Java代码
public class FutureData implements Data {
private RealData realdata = null;
private boolean ready = false;
public synchronized void setRealData(RealData realdata) {
//如果已经准备好直接返回不用再设置
if (ready) {
return; // balk
}
this.realdata = realdata;
//设置值已准备好
this.ready = true;
//唤醒等待线程
notifyAll();
}
public synchronized String getContent() {
//如没有准备好,线程等待
while (!ready) {
try {
wait();
} catch (InterruptedException e) {
}
}
return realdata.getContent();
}
}
获取数据代理类
Java代码
public class Host {
public Data request(final int count, final char c) {
System.out.println(" request(" + count + ", " + c + ") BEGIN");
// (1) 建立FutureData的实体
final FutureData future = new FutureData();
// (2) 为了建立RealData的实体，启动新的线程
new Thread() {
public void run() {
RealData realdata = new RealData(count, c);
future.setRealData(realdata);
}
}.start();
System.out.println(" request(" + count + ", " + c + ") END");
// (3) 取回FutureData实体，作为传回值
return future;
}
}
//测试类
Java代码
public class Main {
public static void main(String[] args) {
System.out.println("main BEGIN");
Host host = new Host();
//请求数据
Data data1 = host.request(10, 'A');
Data data2 = host.request(20, 'B');
Data data3 = host.request(30, 'C');
System.out.println("main otherJob BEGIN");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
}
System.out.println("main otherJob END");
//不需要直接等待返回,可以同时去执行别的任务
System.out.println("data1 = " + data1.getContent());
System.out.println("data2 = " + data2.getContent());
System.out.println("data3 = " + data3.getContent());
System.out.println("main END");
}
}
1.异步方法调用返回值
2.分离 "准备返回值"与"使用返回值"
3.变形--不让人等待的Future参与者
4.变形--会改变的Future参与者
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