How to Sort a 2D Array in Java by the Values in the First Column?

Sorting 2D Array based on First Column Values using Java Arrays.sort

In Java, sorting a 2D array based on the values of a specific column can be achieved using the overloaded Arrays.sort(T[] a, Comparator c) method that accepts a Comparator as its second argument.

Consider the following example, where we have a 2D array myArr containing pairs of doubles:

double[][] myArr = new double[mySize][2];
// populate myArr with data

To sort this array based on the first column values, we can use the Comparator interface to define a custom comparison rule:

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

We can then pass this Comparator to the Arrays.sort method:

java.util.Arrays.sort(myArr, comparator);

Alternatively, in Java 8 or later, we can use a lambda function instead of the anonymous inner class for the Comparator:

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

After sorting, the myArr will be sorted based on the values in the first column. The result will be:

[
  {1.0, 5.0},
  {12.0, 100.6},
  {12.1, 0.85},
  {13.0, 1.55}
]

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