从java中的内部类访问外部类

Question

我从Java内部类和静态嵌套类中了解内部类和嵌套类

但是任何人都可以告诉我Inner.redo1()和Inner.redo2()之间的区别是什么？

或者Inner.print1()和Inner.print2()是一样的吗？

public class Outer {
    private String str = "outer";
    public void print() {
      System.out.println("a");
    }

    public class Inner {
        public void redo1() {
            print();
        }
        public void redo2() {
            Outer.this.print();
        }
    }
}

PS:在java.util.ArrayList.Itr #remove中

public void remove() {
    if (lastRet < 0)
        throw new IllegalStateException();
    checkForComodification();

    try {
        ArrayList.this.remove(lastRet);
        cursor = lastRet;
        lastRet = -1;
        expectedModCount = modCount;
    } catch (IndexOutOfBoundsException ex) {
        throw new ConcurrentModificationException();
    }
}

它为什么使用ArrayList.this.remove(lastRet);但不是remove(lastRet);？

Answer 1

但是任何人都可以告诉我Inner.redo1()和Inner.redo2()之间的区别是什么？

Inner.redo1()并且Inner.redo2()确实是一样的.没有语义或功能差异.redo2更明确.就这些.

让我们比较每个方法的字节码:

?  Desktop  javap -c Outer.Inner
Compiled from "Outer.java"
public class Outer$Inner extends java.lang.Object{
final Outer this$0;

public Outer$Inner(Outer);
  Code:
   0:   aload_0
   1:   aload_1
   2:   putfield    #1; //Field this$0:LOuter;
   5:   aload_0
   6:   invokespecial   #2; //Method java/lang/Object."<init>":()V
   9:   return

public void redo1();
  Code:
   0:   aload_0
   1:   getfield    #1; //Field this$0:LOuter;
   4:   invokevirtual   #3; //Method Outer.print:()V
   7:   return

public void redo2();
  Code:
   0:   aload_0
   1:   getfield    #1; //Field this$0:LOuter;
   4:   invokevirtual   #3; //Method Outer.print:()V
   7:   return

}

相同的字节码,相同的最终结果,相同的一切.

为什么使用ArrayList.this.remove(lastRet); 但不删除(lastRet); ？

消除remove()实际应该调用哪个类的方法的歧义.在这种情况下实际上是必要的!没有明确指定ArrayList.this.remove(lastRet),代码不编译:

?  Desktop  javac java/util/ArrayList.java
java/util/ArrayList.java:810: remove() in java.util.ArrayList<E>.Itr cannot be applied to (int)
                remove(lastRet);
                ^
1 error