Arrays

Creating arrays

An array is a fixed length container.

We can create an array of numbers like this:

public class Main {
  public static void main(String[] args) {
    int[] ages = {21, 25, 30};
  }
}

We can create and print an array of strings like this:

java

import java.util.Arrays;

public class Main {
  public static void main(String[] args) {
    String[] bookTitles = {
        "Things Fall Apart",
        "Beloved",
        "One Hundred Years of Solitude",
        "The God of Small Things",
        "Persepolis"
    };

    System.out.println(Arrays.toString(bookTitles));
  }
}

output

[Things Fall Apart, Beloved, One Hundred Years of Solitude, The God of Small Things, Persepolis]

Accessing items

We can access an item using its index.

public class Main {
  public static void main(String[] args) {
    String[] bookTitles = {
        "Things Fall Apart",
        "Beloved",
        "One Hundred Years of Solitude",
        "The God of Small Things",
        "Persepolis"
    };

    var firstBook = bookTitles[0];
    var secondBook = bookTitles[1];

    System.out.println(firstBook); // Things Fall Apart
    System.out.println(secondBook); // Beloved
  }
}

WARNING

Note that we start counting indices from 0. This is known as 0 based indexing.

Array length

We can get the length of an array using the .length property. This is useful for accessing the last element of the Array.

public class Main {
  public static void main(String[] args) {
    String[] bookTitles = {
        "Things Fall Apart",
        "Beloved",
        "One Hundred Years of Solitude",
        "The God of Small Things",
        "Persepolis"
    };

    System.out.println(bookTitles.length); // 5

    var lastItem = bookTitles[bookTitles.length - 1];
    System.out.println(lastItem); // Persepolis
  }
}

Modifying items

We can modify an array item by assigning to its position.

java

import java.util.Arrays;

public class Main {
  public static void main(String[] args) {
    String[] bookTitles = {
        "Things Fall Apart",
        "Beloved",
        "One Hundred Years of Solitude",
        "The God of Small Things",
        "Persepolis"
    };

    bookTitles[2] = "The Kite Runner";

    System.out.println(Arrays.toString(bookTitles));

  }
}

output

[Things Fall Apart, Beloved, The Kite Runner, The God of Small Things, Persepolis]