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限定子类必须包含某个对象实例

2010-11-26 12:10:16| 分类： java | 标签： |举报 |字号大中小订阅

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由于子类被new 的时候必须调用父类的构造函数，默认情况下无参数的构造函数将被调用，但如果此函数为private ，那么就要求子类显示的调用其他构造函数，于是可以这么设计父类：
public abstract class FatherClass{
      private MustHasClass mhc;
      private FatherClass(){}
      public FatherClass(MustHasClass mh){
            mhc=mh;
      }
}
如此一来，子类就必须显示的调用 FatherClass(MustHasClass mh) 这个构造函数了。
如：
public class ChildClass extends FatherClass{
       public ChildClass (MustHasClass mc,String name){
                super(mc);
       }
       public ChildClass (MustHasClass mc,String name,int age){
                super(mc);
       }
}
注意：每个构造函数都必须显示调用super(MustHasClass mh)。

不过暂时没发觉这样做有什么太大的意义，还请高手点明。

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