Can You Access? HackerRank solution in Java | Inner Class in Java

Can You Access HackerRank Solution

Problem Description :

You are given a class Solution and an inner class Inner.Private. The main method of class Solution takes an integer num as input. The powerof2 in class Inner.Private checks whether a number is a power of 2. You have to call the method powerof2 of the class Inner.Private from the main method of the class Solution.

Sample Input and Output :

Input :

8

Output :

8 is power of 2
An instance of class: Solution.Inner.Private has been created

This problem solution based on Inner class. Learn more about Inner class in Java.

• Inner classes and its 4 types with example

Solution :

import java.io.*;
import java.lang.reflect.*;
import java.util.*;
import java.util.regex.*;
import java.security.*;


public class Solution {

    public static void main(String[] args) throws Exception {
        DoNotTerminate.forbidExit();   

        try{
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            int num = Integer.parseInt(br.readLine().trim());
            Object o;// Must be used to hold the reference of the instance of the class Solution.Inner.Private

            o = new Inner().new Private();
            System.out.println(num + " is " + ((Inner.Private)o).powerof2(num));      

        System.out.println("An instance of class: " + o.getClass().getCanonicalName() + " has been created");
       
        }//end of try
       
        catch (DoNotTerminate.ExitTrappedException e) {
            System.out.println("Unsuccessful Termination!!");
        }
    }//end of main
    static class Inner{
        private class Private{
            private String powerof2(int num){
                return ((num&num-1)==0)?"power of 2":"not a power of 2";
            }
        }
    }//end of Inner
    
}//end of Solution

class DoNotTerminate { //This class prevents exit(0)
    
    public static class ExitTrappedException extends SecurityException {

        private static final long serialVersionUID = 1L;
    }
 
    public static void forbidExit() {
        final SecurityManager securityManager = new SecurityManager() {
            @Override
            public void checkPermission(Permission permission) {
                if (permission.getName().contains("exitVM")) {
                    throw new ExitTrappedException();
                }
            }
        };
        System.setSecurityManager(securityManager);
    }
}  

Solution explanation :

For solution understanding, you must have knowledge of inner class in Java. Click on above given link and learn about inner classes.

• We must have to hold the reference of instance of the class Solution.Inner.Private into o.
• So we are holding the reference. o = new Inner().new Private().
• After in println function we are calling powerof2() method using o reference.

Happy learning... Happy Learning...

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