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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 调用方法是不能引用一个实例变量
1 package arkblue.lang.javapuzzler.n53; 2 3 class Thing { 4 public Thing(int i) { 5 6 } 7 } 8 9 public class MyThing extends Thing { 10 private final int arg; 11 12 public MyThing() { 13 super(arg = Math.round(12L)); //编译失败 14 } 15 16 }
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
1 class SomeOtherClass { 2 static int func() { 3 return Math.round(12L); 4 } 5 } 6 7 public class MyThing extends Thing { 8 private final int arg; 9 10 public MyThing() { 11 this(SomeOtherClass.func()); 12 } 13 14 private MyThing(int i) { 15 super(i); 16 arg = i; 17 } 18 }
转-Cannot refer to an instance field arg while explicitly invoking a constructor
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