Careeroza

The Arrays Class

Useful Methods

MethodDoes
Arrays.toString(arr)readable text like [1, 2, 3]
Arrays.deepToString(arr2d)readable text for 2D arrays
Arrays.sort(arr)sorts ascending (in place)
Arrays.binarySearch(arr, key)finds key in a sorted array
Arrays.fill(arr, value)sets every element
Arrays.copyOf(arr, n)new array of length n
Arrays.copyOfRange(arr, from, to)part of an array
Arrays.equals(a, b)compares contents
Arrays.stream(arr).sum()sum (and max, average...)

Example

Example

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        int[] scores = {45, 12, 89, 33, 67};
        System.out.println(Arrays.toString(scores));

        Arrays.sort(scores);
        System.out.println("Sorted: " + Arrays.toString(scores));
        System.out.println("Index of 67: " + Arrays.binarySearch(scores, 67));

        int[] top3 = Arrays.copyOfRange(scores, 2, 5);
        System.out.println("Top 3: " + Arrays.toString(top3));

        int[] bigger = Arrays.copyOf(scores, 7);
        System.out.println("Copy: " + Arrays.toString(bigger));

        char[] stars = new char[5];
        Arrays.fill(stars, '*');
        System.out.println(new String(stars));

        int[] a = {1, 2, 3}, b = {1, 2, 3};
        System.out.println((a == b) + " " + Arrays.equals(a, b));
        System.out.println("Sum: " + Arrays.stream(a).sum());

        String[] names = {"Zoya", "Aman", "Kiran"};
        Arrays.sort(names);
        System.out.println(Arrays.toString(names));
        System.out.println(Arrays.deepToString(new int[][] {{1, 2}, {3, 4}}));
    }
}

Output

[45, 12, 89, 33, 67]
Sorted: [12, 33, 45, 67, 89]
Index of 67: 3
Top 3: [45, 67, 89]
Copy: [12, 33, 45, 67, 89, 0, 0]
*****
false true
Sum: 6
[Aman, Kiran, Zoya]
[[1, 2], [3, 4]]

Note: Printing an array directly shows its type and an internal code like [I@1b6d3586 (it changes every run). Always use Arrays.toString().