Java: Sorting a 2D array by first (int filled) column

Question

I want to sort an Object[][] by the first column which consists of ints. Take, for example, this array:

Object[][] array = {{1, false, false}, {2, true, false}, {0, true, true}};

Now, I want to create a new array whose rows are sorted in a way that the first element of each row ascends:

Object[][] newArray = ...;
System.out.println(Arrays.deepToString(newArray));

What it should print: {{0, true, true}, {1, false, false}, {2, true, false}}

Thank you.

Answer 1

Arrays.sort(array, new Comparator<Object[]>() {
  @Override
  public int compare(Object[] o1, Object[] o2) {
    Integer i1 = (Integer) (o1[0]);
    Integer i2 = (Integer) (o2[0]);
    return i1.compareTo(i2);
  }
});

Answer 2

Arrays in java has a sort method that takes in Comparator as 2nd parameter. You can pass in the parameter to be considered for sorting. In your case, we'll need to sort based on the first parameter of the input 2d array; the solution would look like:

Arrays.sort(array, Comparator.comparingInt(a -> a[0]));

https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html