从内部类的实例访问外部类属性

发布于 2024-08-11 20:13:11 字数 660 浏览 1 评论 0原文

给出以下代码：

public class Outer
{
   public final int n;
   public class Inner implements Comparable<Inner>
   {
      public int compareTo(Inner that) throws ClassCastException
      {
          if (Outer.this.n != Outer.that.n) // pseudo-code line
          {
               throw new ClassCastException("Only Inners with the same value of n are comparable");
//...

我可以用伪代码行交换什么，以便可以比较内部类的两个实例的 n 值？

尝试明显的解决方案 (n != that.n) 无法编译：

Outer.java:10: cannot find symbol
symbol  : variable n
location: class Outer.Inner
                    if (n != that.n) // pseudo-code line

原文

Given the following code:

public class Outer
{
   public final int n;
   public class Inner implements Comparable<Inner>
   {
      public int compareTo(Inner that) throws ClassCastException
      {
          if (Outer.this.n != Outer.that.n) // pseudo-code line
          {
               throw new ClassCastException("Only Inners with the same value of n are comparable");
//...

What can I swap out with my pseudo-code line so that I can compare the values of n for the two instances of the Inner class?

Trying the obvious solution (n != that.n) doesn't compile:

Outer.java:10: cannot find symbol
symbol  : variable n
location: class Outer.Inner
                    if (n != that.n) // pseudo-code line

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﹉夏雨初晴づ 2024-08-18 20:13:11

与实例方法和变量一样，内部类与其封闭类的实例相关联，并且可以直接访问该对象的方法和字段。 - Java OO

你可以在内部类，返回外部类的n。

Inner 上的方法：

public int getOuterN() { return n; }

然后使用此方法进行比较：

getOuterN() != that.getOuterN()

As with instance methods and variables, an inner class is associated with an instance of its enclosing class and has direct access to that object's methods and fields. - Java OO

You could write a getter method in the inner class, which returns n of the outer class.

Method on Inner: