How to read array of integers from the standard input in Java?

Question

in one line from the standard input I have 3 types of integers: the first integer is id, the second integer is N - some number, and after that follows N integers, separeted by a single space which I want to store in array or ArrayList. How can I do this using BufferedReader? I have the following code:

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String[] line = br.readLine().split(" ");
int ID = Integer.parseInt(line[0]);
int N = Integer.parseInt(line[1]);

My question is is there any elegant way to read the rest of the line and to store it into array?

the following N integers are separated just by a single space " " — sammy333
– sammy333, Commented Jul 1, 2014 at 18:51
Using split with a restrictive pattern (exactly one space) requires a very accurately prepared input. If you remain with this approach, splitting on a sequence of white space is recommended ("\\s+"). — laune
– laune, Commented Jul 1, 2014 at 18:55

Ayush · Accepted Answer · 2014-07-01 18:49:24Z

5

Use Scanner and method hasNextInt()

Scanner scanner = new Scanner(System.in);

while (scanner.hasNext()) {

     if (scanner.hasNextInt()) {
        arr[i]=scanner.nextInt();
        i++;
     }
  }

answered Jul 1, 2014 at 18:49

Ayush

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2 Comments

Ayush Over a year ago

This is a general method I've posted. The OP hasn't mentioned his problem specifically. And what's the problem in reading till end of the file if the file contains all integers @laune

laune Over a year ago

OP has explicitly requested how to read "N - some number, and after that follows N integer" and how to store them into an array or list. His "one line from standard input" is not his only line.

arshajii · Accepted Answer · 2014-07-01 18:58:01Z

4

How can I do this using BufferedReader?

You've already read/split the line, so you can just loop over the rest of the inputted integers and add them to an array:

int[] array = new int[N];  // rest of the input

assert line.length + 2 == N;  // or some other equivalent check

for (int i = 0; i < N; i++)
    array[i] = Integer.parseInt(line[i + 2]);

This will also let you handle errors within the loop (I'll leave that part to you, should you find it necessary).

edited Jul 1, 2014 at 18:58

answered Jul 1, 2014 at 18:50

arshajii

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2 Comments

laune Over a year ago

A check whether there are enough elements in String[] line is recommended.

arshajii Over a year ago

@laune Sure, I incorporated that into the answer.

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