Read integers separated with whitespace into int[] array

Question

I read line with

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
reader.readLine();

Example input is

Answer 1

Since you don't know the size of input, you can read input as string and then parse the string array to integer array

String[] arr=reader.readLine().split(" ");
int[] intarr=new int[arr.length];

for(int i=0;i<arr.length;i++)
 intarr[i]=Integer.parseInt(arr[i]);

Answer 2

Simple answer would be read integer inside the for loop using nextInt() method of scanner class.

Here is the implementation :

import java.util.Scanner;

public class DriverMain {
    public static void main(String args[]){
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("Enter the size of an array: ");
        int size = scanner.nextInt();

        System.out.println("Enter array elements separated by single space.");
        int[] numbers = new int[size];
        for(int i=0;i<size;i++){
            numbers[i] =  scanner.nextInt();
        }

        for(int i=0;i<size;i++){
            System.out.println(numbers[i]);
        }

    }
}

Answer 3

You could pre-compiled regex Pattern also to split String.

    Pattern pattern = Pattern.compile("(\\d+)\\s+"); //$NON-NLS-1$
    Matcher matcher = pattern.matcher(line);
    List<Integer> numbers = new LinkedList<Integer>();

    while (matcher.find()) {
        numbers.add(Integer.valueOf(matcher.group(1)));
    }
    Integer[] output = numbers.toArray(new Integer[numbers.size()]);

Or you could also use pattern.split directly

    Pattern pattern = Pattern.compile("(\\d+)"); //$NON-NLS-1$
    String[] numberAsString = pattern.split(line);
    int[] numbers = new int[numberAsString.length];
    for (int i = 0; i < numberAsString.length; i++) {
        numbers[i] = Integer.valueOf(numberAsString[i]).intValue();
    }

Gotta love regex :D

Answer 4

 Scanner sc = new Scanner(System.in);
    String n=sc.nextLine();
    String[] no=n.split(" ");
    int sum=0;
    for(String i:no){
        sum+=Integer.parseInt(i);}
    System.out.println(sum);

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The Above code is how can you take space separate integer inputs using java programming and perform any task of your choice in my case I have added the numbers.

Answer 5

try

 line = reader.readLine();
 String[] s = line.split(" ");
 ...

you can look to StringTokenizer also, but one of the fastest will be to read bytes and iterate them and convert the ascii (utf8?) coded numbers yourself ;)

Answer 6

Well, with Java 8 Streams this can actually be done in one line:

int[] array = Arrays.stream(reader.readLine().split("\\s")).mapToInt(Integer::parseInt).toArray();

where reader is your BufferedReader object.

Explanation:

• reader.readLine() reads the input as String
• reader.readLine().split("\\s") splits that String on white-spaces returning a String[]
• Arrays.stream(reader.readLine().split("\\s")) creates a Stream from that String[]
• Arrays.stream(reader.readLine().split("\\s")).mapToInt(Integer::parseInt) applies Integer::parseInt to each element of that Stream and returns an IntStream consisting of the results of the applied function
• Arrays.stream(reader.readLine().split("\\s")).mapToInt(Integer::parseInt).toArray() returns the int[] containing the elements of that IntStream