java - 修改Java内部类中的变量

Question

我有一个关于 Java 内部类的问题，我无法弄清楚。假设你有

class Outer
{
     int outer = 0;
     class Inner
     {
          int inner = Outer.this.outer; //(or just outer as it is not shadowed)
          inner = 3; //or whatever, even outer = 3
     }
}

好吧，当我写最后一个作业时，我收到编译错误

Syntax error on token ";", , expected

在前一行。

为什么我无法修改内部？

谢谢!

Answer 1

不能在方法之外有语句。一种技术是使用实例初始化 block :

class Outer
{
     int outer = 0;
     class Inner
     {
          int inner = Outer.this.outer; //(or just outer as it is not shadowed)
          // instance initializer block:
          {
              inner = 3; //or whatever, even outer = 3
          }
     }
}

或者，定义一个构造函数:

class Outer
{
     int outer = 0;
     class Inner
     {
          int inner = Outer.this.outer; //(or just outer as it is not shadowed)
          Inner() {
              inner = 3; //or whatever, even outer = 3
          }
     }
}