error occuring while passing array

Question

i am new in java coming from c++ and C. when i pass simply arr= 4 gives correct ouptput but when i pass arr[i]=4 it gives error. could someone tell me and correct me?

code :

package GA;

import java.util.Scanner;

public class ReversedBinary {
    public static void main(String[] args) {
        int number = 0; 
        int i=1;
        int[]arr = new int[]{4};
       // arr[i]4;
    //    number=arr[i];

        if (number <0)
            System.out.println("Error: Not a positive integer");
        else { 

            System.out.print("Convert to binary is:");
            System.out.print(binaryform(arr[i])); // error occuring
        }
    }

    private static Object binaryform(int arr) {
        int remainder;
        if (arr <=1) {
            System.out.print(arr);
            return null;   // KICK OUT OF THE RECURSION
        }

        remainder= arr %2; 
        binaryform(arr >>1);
        System.out.print(remainder);
        return "";

    }
}

error:

Convert to binary is:Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
    at GA.ReversedBinary.main(ReversedBinary.java:18)

Unrelated to your actual issue, but binaryForm has no reason to return Object so its return type should be void, or perhaps String (if you wanted the binary returned instead of printed). — kviiri
– kviiri, Commented May 8, 2014 at 19:52

Alexandre FILLATRE · Accepted Answer · 2014-05-08 19:50:05Z

2

In Java, array indexes start at 0 :

int[] array = new int[]{4};
boolean valid = array[0] == 4; // Valid
boolean invalid = array[1] == 4; // Invalid

So what you need to do is initialize i with the value 0.

answered May 8, 2014 at 19:50

Alexandre FILLATRE

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rahul pasricha · Accepted Answer · 2014-05-08 19:48:55Z

public class ReversedBinary {
    public static void main(String[] args) {
        int number = 0;
        int i=0;  // i is initialized to zero
        int[]arr = new int[]{4};

        if (number <0)
            System.out.println("Error: Not a positive integer");
        else {

            System.out.print("Convert to binary is:");
            System.out.print(binaryform(arr[i])); // error occuring
        }
    }

    private static Object binaryform(int arr) {
        int remainder;
        if (arr <=1) {
            System.out.print(arr);
            return null;   // KICK OUT OF THE RECURSION
        }

        remainder= arr %2;
        binaryform(arr >>1);
        System.out.print(remainder);
        return "";

    }
}

Try this.

Nielarshi · Accepted Answer · 2014-05-08 19:51:08Z

1

ur array arr[] has only 1 element in it

and ur value of i is 1

u are passing arr[1] to the method which doesn't exist for ur array arr.

When u are doing arr = 4 , it means u are assigning 4 to the arr[0].

When u had declared

int[] arr = new int[]{4}, u have pushed and fixed only 1 element in the array arr.

so,

u cant push or assign any value to arr[1] , because it is not in array / cant be pushed in array.

Try changing it as ,

int arraysize = //some integer value
int[] arr = new int[arraysize]

, note : arraysize is some int value which is the maximum element ur array can have.

or change the value of i ,

int i = 0;

answered May 8, 2014 at 19:51

Nielarshi

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2 Comments

user3508182 Over a year ago

i was about to edit my anwer for explain, but thanks to nielarshi, i hope reader could have understood

user3440716 Over a year ago

yea thnaks both of you and to all. these smaller mistakes for beginners takes time away. same happend with me.

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