转-Cannot refer to an instance field arg while explicitly invoking a constructor

编译失败：

Cannot refer to an instance field arg while explicitly invoking a constructor  调用方法时不能引用一个实例变量

 package arkblue.lang.javapuzzler.n53;

 class Thing {
     public Thing(int i) {

     }
 }

 public class MyThing extends Thing {
     private final int arg;

     public MyThing() {
         super(arg = Math.round(12L)); //编译失败
     }

 }

解决办法:使用了交替构造器调用机制（alternate constructor invocation）

在这个私有构造器中，表达式SomeOtherClass.func()的值已经被捕获到了变量i中，并且它可以在超类构造器返回之后存储到final类型的域arg中

 class SomeOtherClass {
     static int func() {
         return Math.round(12L);
     }
 }

 public class MyThing extends Thing {
     private final int arg;

     public MyThing() {
         this(SomeOtherClass.func());
     }

     private MyThing(int i) {
         super(i);
         arg = i;
     }
 }