ArrayList

In this chapter you will learn:

What is Java ArrayList
A quick demo for ArrayList

ArrayList Class

ArrayList is a resizable-array implementation of the List interface.

The ArrayList class extends AbstractList and implements the List interface.

ArrayList supports dynamic arrays that can grow as needed. An ArrayList is a variable-length array of object references, whick can dynamically increase or decrease in size.

ArrayList is a generic class that has declaration of:

class ArrayList&lt;E>

E specifies the type of objects that the list will hold.

ArrayList demo

A demonstration of an array-based list

import java.util.ArrayList;
import java.util.List;
// j a  va 2  s . co  m
public class Main {
  public static void main(String[] args) {
    List<String> ls = new ArrayList<String>();
    String[] weekDays = { "A", "B", "C", "Wed", "Z", "Y", "X" };
    for (String weekDay : weekDays){
      ls.add(weekDay);
    }
    dump("ls:", ls);
    ls.set(ls.indexOf("Wed"), "Wednesday");
    dump("ls:", ls);
    ls.remove(ls.lastIndexOf("X"));
    dump("ls:", ls);
  }
  static void dump(String title, List<String> ls) {
    System.out.print(title + " ");
    for (String s : ls){
      System.out.print(s + " ");
    }
      
    System.out.println();
  }
}