﻿ Java programming exercises: Given two non-negative integers represented as string, return their sum - w3resource

# Java Exercises: Given two non-negative integers represented as string, return their sum

## Java Basic: Exercise-189 with Solution

Write a Java program to given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

Pictorial Presentation: Sample Solution:

Java Code:

``````import java.util.*;
public class Solution {
public static void main(String[] args) {
String n1 = "123";
String n2 = "456";
System.out.println("'" + n1 + "'" + " + " + "'" + n2 + "'" + " = " + addStrings(n1, n2));
}
public static String addStrings(String n1, String n2) {
int[] x = str_num(n1);
int[] y = str_num(n2);
int[] sum = new int[Math.max(x.length, y.length) + 1];
int z = 0;
int index = sum.length - 1;
int i = 0;
int j = 0;
while (index >= 0) {
if (i < x.length) {
z += x[i++];
}
if (j < y.length) {
z += y[j++];
}
sum[index--] = z % 10;
z /= 10;
}
StringBuilder sb = new StringBuilder(sum.length);
for (i = (sum == 0 ? 1 : 0); i < sum.length; ++i) {
sb.append(sum[i]);
}
return sb.toString();
}

private static int[] str_num(String num) {
char[] digits = num.toCharArray();
int[] number = new int[digits.length];
int index = number.length - 1;
for (char digit: digits) {
number[index--] = digit - '0';
}
return number;
}
}
```
```

Sample Output:

```'123' + '456' = 579
```

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