Accessing outer class from inner class in java

Questions

http://stackoverflow.com/questions/70324/java-inner-class-and-static-nested-class/70358 http://stackoverflow.com/questions/70324/java-inner-class-and-static-nested-class/70358

But can any body tell me what s the difference between Inner.redo1() and Inner.redo2()?

Or Inner.print1() and Inner.print2() are the same?

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:    In java.util.ArrayList.Itr#remove

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();
    }
}

Why does it use ArrayList.this.remove(lastRet); but not remove(lastRet); ?

Answers

But can any body tell me what s the difference between Inner.redo1() and Inner.redo2()?

Inner.redo1() and Inner.redo2() are indeed the same. There is no semantic or functional difference. redo2 is more explicit. That is all.

Let s compare each method s bytecode:

λ  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

}

Same bytecode, same end result, same everything.

---

Why does it use ArrayList.this.remove(lastRet); but not remove(lastRet); ?

To disambiguate which class remove() method should actually be called. It is actually necessary in this case! Without explicitly specifying ArrayList.this.remove(lastRet), the code does not compile:

λ  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

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/16409210/accessing-outer-class-from-inner-class-in-java

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