Sum Integers written into a String

Question

I used

int num = Integer.parseInt(str)

to written integer values into a string.I need a function that reads these values from given string and calculates their sum.

Example: input - "43 68 9 23 318" output - 461

Answer 1

String str = "43 68 9 23 318";
int num = Integer.parseInt(str)

What you are doing is, trying to parse the complete input string at once, that will throw the NumberFormatException. You need to split it first and then perform the sum on each returned String.

---

Split the input string by whitespace then parse each number and perform the sum.

public static void main(String[] args) {
  String input = "43 68 9 23 318";
  String numbers[] = input.split("\\s+");   // Split the input string.
  int sum = 0;
  for (String number : numbers) {  // loop through all the number in the string array
    Integer n = Integer.parseInt(number);  // parse each number
    sum += n;     // sum the numbers
  }
  System.out.println(sum);  // print the result.
}

Answer 2

In Java 8, using streams

String input = "43 68 9 23 318";
String numbers[] = input.split("\\s+");
int[] nums = Arrays.stream(numbers.substring(1, numbers.length()-1).split(","))
    .map(String::trim).mapToInt(Integer::parseInt).toArray();
int sum = IntStream.of(nums).sum();
System.out.println("The sum is " + sum);

Answer 3

Another Java 8 way:

public void test() {
    String str = "43 68 9 23 318";
    int sum = Pattern.compile(" ")
            .splitAsStream(str)
            .mapToInt(Integer::parseInt)
            .sum();
    System.out.println("sum:" + sum);
}

Answer 4

You can try following with java-8. Here we first split the String to get String[] with number String (i.e ["43", "68", "9", "23", "318"]) and then with the help of Arrays.stream we can map all those Strings to Integer and we will have IntStream and from that we can get sum of all streamed Integer values.

public class Test {

    public static void main(String[] args) {
        String input = "43 68 9 23 318";
        int sum = Arrays.stream(input.trim().split("\\s+"))
                        .mapToInt(Integer::parseInt)
                        .sum();
        System.out.println(sum);
    }
}    

OUTPUT

461

Answer 5

If you don't want to go to the hassle of splitting it you can do it in-place:

public void test() {
    String str = "43 68 9 23 318";
    int sum = 0;
    int value = 0;
    for (int i = 0; i < str.length(); i++) {
        char ch = str.charAt(i);
        switch (ch) {
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                value = value * 10 + (ch - '0');
                break;
            default:
                sum += value;
                value = 0;
                break;

        }

    }
    // Remember the last number.
    sum += value;
    value = 0;
    System.out.println("sum:" + sum);
}

Answer 6

This is the needed Working copy with function

    public class Main {
            /*This function is static because we called it from static main*/
        public static int returnSum(String str)
        {
            String []numbStr = str.split(" ");
            int sum = 0;

            for(String temp:numbStr)
            {
                 sum += Integer.parseInt(temp);
            }

            return sum;
        }

        public static void main(String... args)
        {
            String str = "43 68 9 23 318";
                    /*Note that we can call only static functions from main when directly calls*/ 
            int result =  returnSum(str);

            System.out.println(result);

        }
    }

Answer 7

Java 8 Streams in one line

Arrays.stream(text.split(" ")).mapToInt(Integer::parseInt).sum();

Answer 8

This works not only for the strings that contains numbers separated by spaces but also for the strings containing characters others than numbers like "abc10jh20"-->30

 import java.util.Arrays.*;
    public class HelloWorld{
        //this code works also if the string contains alphabets not just spaces
    static int count,sum;
         public static void main(String []args){
             String str="123 10 7";//getting input in form of string
             int length=str.length();
             for(int i=0;i<=length-1;i=i+count+1)
             {
                 count=0;
                 if(Character.isDigit(str.charAt(i)))
                 {
                     for(int j=i;j<=length-1;j++)
                     {
                         if(Character.isDigit(str.charAt(j)))
                         {
                             count++;//to find the length of the number

                         }
                         else{
                             break;
                         }

                     }
                     String str2=str.substring(i,i+count);//selecting the substring
                     System.out.println("the parsing string "+str2);//displays strings getting parsed
                     int inc=count+1;

                      sum=sum+Integer.parseInt(str2);//finding sum

                 }

             }
             System.out.println("the sum is "+sum);
         }
    }