中介者的职责太多.
一般应用在一组对象以定义良好但是复杂的方式进行通信的场合.以及想定制一个分布在多个类中的行为,而又不想生成太多子类的场合.
不要先使用中介者,要先考虑设计是否合理.
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| package mediator;
public abstract class Mediator {
public abstract void send(String message, Country country);
}
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| package mediator;
public class UnitedNations extends Mediator {
private China china;
private America america;
public void setChina(China china) {
this.china = china;
}
public void setAmerica(America america) {
this.america = america;
}
@Override
public void send(String message, Country country) {
if (country instanceof China) {
america.receive(message);
} else {
china.receive(message);
}
}
}
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| package mediator;
public class Country {
protected Mediator unitedNations;
public Country(Mediator unitedNations) {
this.unitedNations = unitedNations;
}
}
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| package mediator;
public class China extends Country {
public China(Mediator unitedNations) {
super(unitedNations);
}
public void declare(String message) {
unitedNations.send(message, this);
}
public void receive(String message) {
System.out.println("中国收到: " + message);
}
}
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| package mediator;
public class America extends Country {
public America(Mediator unitedNations) {
super(unitedNations);
}
public void declare(String message) {
unitedNations.send(message, this);
}
public void receive(String message) {
System.out.println("美国收到: " + message);
}
}
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| package mediator;
public class Main {
public static void main(String[] args) {
UnitedNations un = new UnitedNations();
China china = new China(un);
America america = new America(un);
un.setAmerica(america);
un.setChina(china);
america.declare("第三次世界大战");
china.declare("无条件投降");
}
}
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