Question

I need to make a program that adds long integers without using the biginteger class.

I am working on the add method now and I think I have it correct but I am stuck on returning the correct data type for my method and I’m not sure how to correct it.

Here are my 2 classes so far:

Main Class:

import java.util.Scanner;

public class testLargeInteger
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        String string1;
        String string2;
        int exp =0;


        System.out.print("Enter the first integer: ");
        //Store up the input string “string1” entered by the user from the keyboard.
        string1 = input.next(); 

        LargeInteger firstInt = new LargeInteger(string1);

        System.out.print("Enter the second integer: ");
        string2 = input.next(); 
        //Store up the input string “string2” entered by the user from the keyboard.
        LargeInteger secondInt = new LargeInteger(string2);

        System.out.print("Enter the exponential integer: ");
        //Store up the input integer “exp” entered by the user from the keyboard.
        exp = input.nextInt(); 


        LargeInteger sum = firstInt.add(secondInt);

        System.out.printf ("First integer: %s \n", firstInt.display());
        System.out.println("Second integer: " + secondInt.display());
        System.out.println(" Exponent: " + exp);

        System.out.printf (" Sum = %s \n", sum.display());

    }
}

LargeInteger.class:

public class LargeInteger 
{
    private int[] intArray;

    //convert the strings to array
    public LargeInteger(String s) 
    {   
        intArray = new int[s.length()];
        for (int i = 0; i < s.length(); i++) 
            intArray[i] = Character.digit(s.charAt(i), 10); // in base 10
    }

    //display the strings
    public String display() 
    {           
        String result="";

        for (int i = 0; i < intArray.length; i++)      
            result += intArray[i];
        return result.toString();
    }   

    //get first array
    public int[] getIntArray() 
    {
        return intArray;
    }

    public LargeInteger add(LargeInteger secondInt)
    {
        int[] otherValues = secondInt.getIntArray();

        int maxIterations = Math.min(intArray.length, otherValues.length);
        int currentResult; //to store result 
        int[] resultArray = new int[Math.max(intArray.length, otherValues.length) + 1];

        int needToAdd = 0; //to store result should be added next step

        for(int i = 0; i < maxIterations; i++) 
        {
            currentResult = intArray[i] + otherValues[i];
            resultArray[i] = currentResult % 10 + needToAdd; //if more than 9 its correct answer
            needToAdd = currentResult / 10; //this is what you need to add on next step
        }
        resultArray[Math.max(intArray.length, otherValues.length) + 1] = needToAdd;

        return resultArray;
    }
}

Answer 1

You need a second LargeInteger constructor:

public LargeInteger( int[] array ) { 
     intArray = array
}

Then your method can return:

return new LargeInteger( resultArray );