Sum integers in delimited string

Question

Given a delimiter String as input, add all the numbers together.

For example:

addNumbers("12 24 36") -> 72 
addNumbers("12 12 100") -> 124

I am getting number format exception when i try this.

String a="12 34 4 676";
String b=a.replaceAll(" ", "+");
long num=Long.parseLong(a);

Answer 1

Yes, because 12+34+4+676 is not a number, it's an expression.

In Java 8 you could do something like:

final int sum = Stream.of(a.split("\\s")).
        mapToInt(Integer::parseInt).
        sum();

In Java 7 you could do:

int sum = 0;
for (final String s : a.split("\\s")) {
    sum += Integer.parseInt(s);
}

OP's comment: i dont want to use array.

I like a challenge, so here is a solution that uses a Scanner:

final Scanner scanner = new Scanner(a);
int sum = 0;
while(scanner.hasNextInt()) {
    sum += scanner.nextInt();
}

Answer 2

You cannot parse a string that contains operators to directly get the value. Split it using split("\\s") and then loop through the array and find the sum.