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

Sorting a 2D Array by the First Column Using Java's Arrays.sort

In Java, sorting a 2D array based on the values of the first column can be achieved using the overloaded Arrays.sort method that takes a Comparator as a second argument. This Comparator allows you to specify a custom comparison logic for sorting the array elements.

To sort a 2D array using the first column values, you can follow these steps:

Create a Comparator implementation that compares the first elements of the subarrays. This can be done using the Double.compare method for comparing double values:

Comparator<double[]> comparator = (a, b) -> Double.compare(a[0], b[0]);

Call the Arrays.sort method with the array and the Comparator as arguments:

Arrays.sort(array, comparator);

Alternatively, if you're using Java 8 or higher, you can use a lambda function to simplify the Comparator:

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

Example:

Consider the following 2D array myArr:

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

After sorting myArr using the approach described above, it will be sorted based on the first column values:

1      5
12     100.6
12.1   .85
13     1.55

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