How to Sort a 2D Array in Java Using Arrays.sort?

Sorting a 2D Array Using Arrays.sort

Sorting a multidimensional array can be a complex task. However, using Java's Arrays.sort method, it is possible to achieve this efficiently.

Specifically, the solution involves using the overloaded Arrays#Sort(T[] a, Comparator c) method, which takes a Comparator as its second argument. A comparator is an object that defines how objects are compared. In this case, we want to compare the values of the first element in each subarray.

To implement this, create a comparator that implements the java.util.Comparator interface and overrides its compare() method. This method should compare the first elements of the two arrays and return -1, 0, or 1 depending on the order they should appear.

For instance, consider the following 2D array:

double[][] myArr = {
  {1, 5},
  {13, 1.55},
  {12, 100.6},
  {12.1, .85}
};

To sort this array in ascending order based on the values of the first element in each subarray, use the following code:

java.util.Arrays.sort(myArr, new java.util.Comparator<double[]>() {
  public int compare(double[] a, double[] b) {
    return Double.compare(a[0], b[0]);
  }
});

This will produce the following sorted array:

[
  {1, 5},
  {12, 100.6},
  {12.1, .85},
  {13, 1.55}
]

In Java 8 and later, you can use lambdas to simplify the comparator:

Arrays.sort(array, Comparator.comparingDouble(o -> o[0]));

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