need help with two dimensional array that takes input from user and bubble sorts and selections sorts

Thank you. I am having problems with declaring the array. How do i do that without knowing how many elements are going to be input by the user?

Here is a code that performs Bubble Sort using 2 d array.

public class BubbleSortWith2D {

  public static void main(String[] args) {
    int[][] a = {{3,24}, {4,56}, {1, 98}, {2,36}};

    bubbleSort(a);

    for(int i = 0;i<a.length;i++) {
      String s = "";
      for(int j=0;j<a[i].length;j++) s += a[i][j] + " ";
      System.out.println(s);
    }
  }

  public static void bubbleSort(int[][] array) {
    while(true) {
      boolean swapped = false;
      for(int i=0;i<array.length-1;i++) {
        if (array[i][0] > array[i+1][0]) {
          swapped = true;
          for(int j=0;j<array[i].length;j++) {
            int t = array[i][j];
            array[i][j] = array[i+1][j];
            array[i+1][j] = t;
          }
        }
      }
      if (!swapped) return;
    }
  }
}