java - 从内部类的实例访问外部类属性

Question

给定以下代码:

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");
//...

我可以用我的伪代码行交换什么，以便我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

Answer 1

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

你可以在内部类中写一个getter方法，它返回外部类的n。

Inner 上的方法:

public int getOuterN() { return n; }

然后用这个方法比较:

getOuterN() != that.getOuterN()