我尝试使用内部Enum实现了一个Enum样式的工厂模式,但它并没有起作用。 是否有解决方案,而不必将内部Enum分离成新文件? 换句话说,内部Enum样式的工厂模式是否可行?
以下是代码。
public class SampleParent {
private class InnerChild { }
private class InnerChildA extends InnerChild { }
private class InnerChildB extends InnerChild { }
private class InnerChildC extends InnerChild { }
enum InnerChildEnum {
CHILD_A {
@Override
public InnerChild getInstance() {
return new InnerChildA(); // compile error
}
},
CHILD_B {
@Override
public InnerChild getInstance() {
return new SampleParent.InnerChildB(); // compile error
}
},
CHILD_C {
@Override
public InnerChild getInstance() {
return SampleParent.new InnerChildC(); // compile error
}
},
;
public abstract InnerChild getInstance();
}
private static class InnerChildFactoryEnumStyled {
public static InnerChild getInnerChild(InnerChildEnum child) {
return child.getInstance();
}
}
public static void main(String[] args) {
// I want to write this way
InnerChild child = InnerChildFactoryEnumStyled.getInnerChild(InnerChildEnum.CHILD_A);
}
}
编译错误信息如下:
$ javac SampleParent.java
SampleParent.java:12: error: non-static variable this cannot be referenced from a static context
return new InnerChildA();
^
SampleParent.java:18: error: non-static variable this cannot be referenced from a static context
return new SampleParent.InnerChildB();
^
SampleParent.java:24: error: cannot find symbol
return SampleParent.new InnerChildC();
^
symbol: variable SampleParent
3 errors