Java ArrayList

Java ArrayList

An ArrayList is a resizable array in the java.util package. Unlike a plain array, it grows and shrinks as you add and remove items.

Creating an ArrayList

import java.util.ArrayList;

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

The type goes inside angle brackets, like <String>.

Common methods

Example

cars.add("Volvo");
cars.add("BMW");
cars.get(0); // "Volvo"
cars.set(0, "Opel");
cars.size(); // 2

Loop through an ArrayList

for (int i = 0; i < cars.size(); i++) {
  System.out.println(cars.get(i));
}

Or use the for each loop:

for (String i : cars) {
  System.out.println(i);
}

Array vs ArrayList

TL;DR

• ArrayList is a resizable array.
• Use add, get, set, remove, size.
• Loop with size() or a for each loop.