Chapter 7, Problem 11AW

Arraylist:

It is a collection framework and the java package “java.util.package” is used for this. Arraylist is a dynamic list which is used to store dynamic array elements.

To use Arraylist class in a Java program, it must be imported first from the Java library files.

The statement which must be imported in order to use Arraylist class is,

import java.util.Arraylist;

Syntax for Arraylist:

ArrayList() object_name=new ArrayList();

Here,

• “ArrayList()” is the class name with no arguments. The programmer can use “ArrayList(Collection c)” and “ArrayList(int)” from “util” package.
• “object_name” describes name of the object of Arraylist.

Creation of string ArrayList:

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

The above statement is an example of creation of ArrayList class. The array object “x” is used to store the list of objects.

Inserting an item at specific location in an ArrayList object:

The items can be inserted at the specified index in an Arraylist object using “add()” method,

Insertion of object at the beginning of the list is as follows:

a.add (0, object);

The “a” is an array list object and “add” is a built-in function which is used to add the objects to the list. The argument “(0, object)” means add the object at the beginning of the object.

Example:

To insert an item at index 2 for ArrayList named List which stores strings, the following statement is used,

List.add(2, “John”);