Arrays

Syntax

type[] arrayName = new type[size];

Examples

int[] numbers = {10, 20, 30, 40, 50};
String[] names = new String[3];
names[0] = "Fola";
names[1] = "Zain";
names[2] = "Jamal";

System.out.println(numbers[0]);   // 10
System.out.println(numbers.length); // 5
System.out.println(names[1]);      // Zain

int[] scores = {85, 92, 78, 90};

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

// Enhanced for-each loop - simpler when you don't need the index
for (int score : scores) {
    System.out.println(score);
}

int[][] grid = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};

System.out.println(grid[1][2]);  // 6 (row 1, column 2)

for (int[] row : grid) {
    for (int value : row) {
        System.out.print(value + " ");
    }
    System.out.println();
}

import java.util.Arrays;

int[] numbers = {5, 2, 8, 1, 9};

Arrays.sort(numbers);
System.out.println(Arrays.toString(numbers));  // [1, 2, 5, 8, 9]

int[] filled = new int[5];
Arrays.fill(filled, 7);
System.out.println(Arrays.toString(filled));   // [7, 7, 7, 7, 7]

Best practices

• Use an ArrayList instead of a plain array whenever the collection needs to grow or shrink dynamically
• Use the enhanced for-each loop when you just need the values, and a standard indexed loop when you need the index too
• Use Arrays.toString() (or Arrays.deepToString() for 2D arrays) to print array contents readably - printing an array directly shows its memory reference, not its contents
• Always check array.length before accessing an index in a loop to avoid an ArrayIndexOutOfBoundsException

At a glance

Purpose

General-purpose application development

File extension

.java

Runs in

Java Virtual Machine

Usually used with

JDK and Java libraries

Specifications & further reading

• Java Language Specification

Related Java documentation