CODEWITHSUNDEEP
javaencapsulationinner-classesnested-class
Malwinder Singh
Malwinder Singh

Reputation: 7050

How to access outer class variable of same name?

I have made an Outer and an Inner class. Both these classes have variable int x. How to access x of Outer class in inner class. this.x is not working.

class OuterClass {
int x,y;
private class InnerClass {
    private void printSum(int x,int y) {
        this.x=x;
        this.y=y;
    }
  }
}

Upvotes: 5

Views: 3228

Answers (4)

BlackHatSamurai
BlackHatSamurai

Reputation: 23483

If you want to do this you need to first instantiate the outer class, then the inner like so:

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    int x,y,sum;

    public static void main (String[] args) throws java.lang.Exception
    {
        //Create outer object
        Ideone ideOne = new Ideone();

        //instantiate inner object, and call method
        Ideone.InnerClass ic = ideOne.new InnerClass();
        ic.printSum(5,4);
    }


    private class InnerClass {
        private void printSum(int x,int y) {
            //reference the outer object instance
            Ideone.this.x=x;
            Ideone.this.y=y;
            Ideone.this.sum = x + y;
            System.out.println(Ideone.this.sum);
        }
    }
}

This has been tested here: http://ideone.com/e.js/DRIzSg

Output: 9

Upvotes: 1

Kafeaulait
Kafeaulait

Reputation: 684

Use OuterClass.this.x; OuterClass.this references the parent object (from whom the InnerClass object is spawned).

Consider the following overshadowing example posted in the official Oracle tutorial:

public class ShadowTest {

    public int x = 0;

    class FirstLevel {

        public int x = 1;

        void methodInFirstLevel(int x) {
            System.out.println("x = " + x);
            System.out.println("this.x = " + this.x);
            System.out.println("ShadowTest.this.x = " + ShadowTest.this.x);
        }
    }

    public static void main(String... args) {
        ShadowTest st = new ShadowTest();
        ShadowTest.FirstLevel fl = st.new FirstLevel();
        fl.methodInFirstLevel(23);
    }
}

with the output

x = 23
this.x = 1
ShadowTest.this.x = 0

x = 23 refers to the local variable of the method void methodInFirstLevel(), this.x = 1 refers to the public field x of the FirstLevel inner-class, and ShadowTest.this.x = 0 refers to the public field x of the ShadowTest outer-class.

Upvotes: 0

Shineed Basheer
Shineed Basheer

Reputation: 578

Other way is to Make Outer class members as protected

public class OuterClass {

 protected int x=10,y=20;

private class InnerClass {

    private void printSum(int x1,int y1) {
        x=x1;
        y=y1;
    }

  }

 }

Upvotes: -1

Sachin Gupta
Sachin Gupta

Reputation: 8358

You can try this : 

   private void printSum(int x,int y) {
       OuterClass.this.x=x;
       OuterClass.this.y=y;
    }

Upvotes: 8

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