Arrays in Java 1D, 2D, Sorting

Creating and Accessing Arrays

Arrays can be created with values directly or with a fixed size. Access elements using square brackets and a zero-based index.

Array Basics

public class ArrayBasics {
    public static void main(String[] args) {
        int[] marks = {85, 90, 76};
        System.out.println(marks[0]);

        marks[1] = 95;
        System.out.println("Length: " + marks.length);
    }
}

Looping Through Arrays

Use a normal for loop when you need the index. Use enhanced for when you only need values.

Array Traversal

public class ArrayTraversal {
    public static void main(String[] args) {
        String[] names = {"Asha", "Ravi", "Meera"};

        for (int i = 0; i < names.length; i++) {
            System.out.println(i + ": " + names[i]);
        }

        for (String name : names) {
            System.out.println(name.toUpperCase());
        }
    }
}

Searching, Sorting, and Copying

The Arrays utility class provides helper methods for sorting, searching, copying, comparing, and printing arrays.

Arrays Utility Class

import java.util.Arrays;

public class ArraysUtilityDemo {
    public static void main(String[] args) {
        int[] numbers = {5, 1, 9, 3};
        Arrays.sort(numbers);

        System.out.println(Arrays.toString(numbers));
        System.out.println(Arrays.binarySearch(numbers, 9));

        int[] copy = Arrays.copyOf(numbers, numbers.length);
        System.out.println(Arrays.equals(numbers, copy));
    }
}

binarySearch requires the array to be sorted first.

2D and Jagged Arrays

A 2D array is an array of arrays. Rows can have equal length like a matrix, or different lengths like a jagged table.

2D Array

public class MatrixDemo {
    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6}
        };

        for (int row = 0; row < matrix.length; row++) {
            for (int col = 0; col < matrix[row].length; col++) {
                System.out.print(matrix[row][col] + " ");
            }
            System.out.println();
        }
    }
}

Before you move on

Arrays in Java 1D, 2D, Sorting Mastery Check

4 checks

Arrays can be created with values directly or with a fixed size.
Access elements using square brackets and a zero-based index.
Use a normal for loop when you need the index.
Use enhanced for when you only need values.

Array Failure Boundary

Invalid index
Java arrays use indexes from zero through length - 1. Guard calculated indexes and test empty arrays before reading the first or final element.

Core Java Questions Learners Ask

Indexes start at zero, so an array of length n ends at n - 1.

No. Use ArrayList when the number of elements must change.

It creates a new array and copies as many elements as fit.

Previous Next

Arrays in Java 1D, 2D, Sorting

Creating and Accessing Arrays

Array Basics

Looping Through Arrays

Array Traversal

Searching, Sorting, and Copying

Arrays Utility Class

2D and Jagged Arrays

2D Array

Arrays in Java 1D, 2D, Sorting Mastery Check

Array Failure Boundary

Invalid index

Arrays Connections

Core Java Questions Learners Ask

Why does an array index stop at length - 1?

Can a Java array grow after creation?

What does Arrays.copyOf do?

Core Java Resources

Popular Tutorials