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  • Java ArrayList

Java ArrayList

The ArrayList class is a resizable array, which can be found in the java.util package.

The difference between a built-in array and an ArrayList in Java, is that the size of an array cannot be modified (if you want to add or remove elements to/from an array, you have to create a new one). While elements can be added and removed from an ArrayList whenever you want. The syntax is also slightly different:

Example

Create an ArrayList object called cars that will store strings:

import java.util.ArrayList; // import the ArrayList class

 

ArrayList<String> cars = new ArrayList<String>(); // Create an ArrayList object

If you don't know what a package is, read our Java Packages Tutorial.

Add Items

The ArrayList class has many useful methods. For example, to add elements to the ArrayList, use the add() method:

Example

import java.util.ArrayList;

 

public class Main {

  public static void main(String[] args) {

    ArrayList<String> cars = new ArrayList<String>();

    cars.add("Volvo");

    cars.add("BMW");

    cars.add("Ford");

    cars.add("Mazda");

    System.out.println(cars);

  }

}

Access an Item

To access an element in the ArrayList, use the get() method and refer to the index number:

Example

cars.get(0);

Remember: Array indexes start with 0: [0] is the first element. [1] is the second element, etc.

Change an Item

To modify an element, use the set() method and refer to the index number:

Example

cars.set(0, "Opel");

Remove an Item

To remove an element, use the remove() method and refer to the index number:

Example

cars.remove(0);

To remove all the elements in the ArrayList, use the clear() method:

Example

cars.clear();

ArrayList Size

To find out how many elements an ArrayList have, use the size method:

Example

cars.size();

Loop Through an ArrayList

Loop through the elements of an ArrayList with a for loop, and use the size() method to specify how many times the loop should run:

Example

public class Main {

  public static void

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