Java stdin not prompting program to run

Question

I am working on a Merge-sort algorithm, and I am currently trying to test if it works.

It should be controlled through stdin with the input format:

array length element values (separated by " ")

However, when typing in:

3
17 10 3

Nothing happens, and hitting enter, just get me to the next line in the console.

I get no error message (unless I type in wrong input), and so I have a hard time figuring out why the script is not prompted to run with the input given.

(Code is copied below)

package merge;
import java.io.*;
import java.util.*;
public class MergeSort
{
 // This method takes two sorted arrays of integers as input parameters
 // and it should return one sorted array of integers.
 public int[] merge(int[] A1, int[] A2) {
 int[] C = new int[A1.length + A2.length];
 int i = 0, j = 0, k = 0;
 while (i < A1.length && j < A2.length)
 C[k++] = A1[i] < A2[j] ? A1[i++] : A2[j++];
 while (i < A1.length) 
 C[k++] = A1[i++];
 while (j < A2.length) 
 C[k++] = A2[j++];
 return C;
 }
 // This method takes an array of integers as input parameter,
 // and it should then return the integers sorted
 // in ascending order using the MergeSort algorithm.
 private int[] sort(int[] numbers) {
 //pointers
 int i = 0, j = 0, k = 0;
 // reference values
 int half = numbers.length / 2;
 int[] sorted = new int[numbers.length];
 if (numbers.length <= 1){
 return numbers;
 }
 //left part of 'numbers'
 int[] left = new int[half];
 int[] right;
 //right part of 'numbers' 
 if (numbers.length % 2 != 0){
 right = new int[half+1];
 j = half + 1;
 }
 else{
 right = new int[half];
 j = half;
 }
 //fills out left half of array with values from input array
 while (i < half)
 left[i] = numbers[i];
 i++;
 //fills out right half of array with values from input array
 while (j < numbers.length)
 right[j] = numbers[k];
 j++; k++;
 left = sort(left);
 right = sort(right);
 merge(left,right);
 return sorted;
 }
 // ##################################################
 // # Stdin part. #
 // ##################################################
 public static void main(String[] args) throws IOException {
 new MergeSort().run();
 }
 private void run() throws IOException {
 BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
 int[] numbers = readIntArray(in);
 numbers = sort(numbers);
 for (int i = 0; i < numbers.length; i++) {
 System.out.print(numbers[i] + " ");
 }
 }
 private int[] readIntArray(BufferedReader in) throws IOException {
 int length = Integer.parseInt(in.readLine());
 int[] array = new int[length];
 StringTokenizer st = new StringTokenizer(in.readLine());
 for (int i = 0; i < length; i++) {
 array[i] = Integer.parseInt(st.nextToken());
 }
 return array;
 }
}

Answer 1

You call readLine() two times, resulting in an attempt to read two lines on the standard input.