Java Arrays Utility Class: Sorting, Searching, Copying and Printing

The java.util.Arrays class is a powerful utility toolkit containing static helper methods for manipulating, sorting, searching, comparing, and printing Java arrays efficiently.

Essential java.util.Arrays Methods

import java.util.Arrays;

public class ArraysUtilityDemo {
    public static void main(String[] args) {
        int[] scores = { 85, 42, 99, 14, 76 };

        // 1. Arrays.toString() - Clean formatted printing:
        System.out.println("Original: " + Arrays.toString(scores)); // [85, 42, 99, 14, 76]

        // 2. Arrays.sort() - High-speed Dual-Pivot Quicksort:
        Arrays.sort(scores);
        System.out.println("Sorted:   " + Arrays.toString(scores)); // [14, 42, 76, 85, 99]

        // 3. Arrays.binarySearch() - O(log n) lookup (Requires sorted array!):
        int index = Arrays.binarySearch(scores, 76);
        System.out.println("Index of 76: " + index); // Index 2

        // 4. Arrays.copyOf() - Deep cloning and resizing:
        int[] expanded = Arrays.copyOf(scores, 7);
        System.out.println("Expanded (length 7): " + Arrays.toString(expanded)); // [14, 42, 76, 85, 99, 0, 0]

        // 5. Arrays.fill() - Batch initialization:
        int[] flags = new int[5];
        Arrays.fill(flags, 1);
        System.out.println("Filled flags: " + Arrays.toString(flags)); // [1, 1, 1, 1, 1]

        // 6. Arrays.equals() - Value-based equality:
        int[] a1 = { 1, 2, 3 };
        int[] a2 = { 1, 2, 3 };
        System.out.println("Arrays equal: " + Arrays.equals(a1, a2)); // true
    }
}

Multidimensional Array Printing: Arrays.deepToString()

Calling standard Arrays.toString() on a 2D array merely prints internal memory hashcodes. Use Arrays.deepToString() for formatted 2D/3D grids:

int[][] matrix = { { 1, 2 }, { 3, 4 } };
System.out.println(Arrays.deepToString(matrix)); // [[1, 2], [3, 4]]