What is an Arraylist used for?

Answer 1

An ArrayList is a data structure. It stores data in an array that can be dynamically resized. This data structure in Microsoft .NET Framework contains Methods that assist the programmer in accessing and storing data within the ArrayList. The following link explains the .NET ArrayList class. http://msdn2.microsoft.com/en-us/library/system.collections.arraylist(vs.80).aspx

Answer 2

java.util.ArrayList is a collection class that is used to hold a collection of objects.

ex: ArrayList lst = new ArrayList();

The above line creates a new ArrayList of name lst

You can add objects to it by using the add method.

Ex: lst.add(object);

An ArrayList can have any number of elements. You can get the object at a specified position by using the get method

Ex: Object obj = lst.get(1);

It is fast and easy to use.

Note: It is not thread safe so do not use them in multi-threaded programming. Use Vectors instead.

Answer 3

An Array List in Java is a way of structuring data and in one of several ways of structuring data. It cannot be dynamically resized and does not support search and sort while other data structures do.

Answer 4

The java.util.ArrayList class is one of the most commonly used of all the classes in the Collections Framework. Some of the advantages ArrayList has over arrays are

• It can grow dynamically.

• It provides more powerful insertion and search mechanisms than arrays.

Let's take a look at using an ArrayList that contains Strings. A key design goal of the Collections Framework was to provide rich functionality at the level of the main interfaces: List, Set, and Map. In practice, you'll typically want to instantiate an ArrayList polymorphically like this:

List myFirstArrayList = new ArrayList();

As of Java 5 you'll want to say

List myFirstArrayList = new ArrayList();

This kind of declaration follows the object oriented programming principle of "coding to an interface", and it makes use of generics. We'll say lots more about generics in future, but for now just know that, as of Java 5, the syntax is the way that you declare a collection's type. (Prior to Java 5 there was no way to specify the type of a collection, and when we cover generics, we'll talk about the implications of mixing Java 5 (typed) and pre-Java 5 (untyped) collections.)

In many ways, ArrayList is similar to a String[] in that it declares a container that can hold only Strings, but it's more powerful than a String[]. Let's look at some of the capabilities that an ArrayList has

List test = new ArrayList();

String s = "hi";

test.add("string");

test.add(s);

test.add(s+s);

System.out.println(test.size());

System.out.println(test.contains(42));

System.out.println(test.contains("hihi"));

test.remove("hi");

System.out.println(test.size());

which produces

3

false

true

2

There's lots going on in this small program. Notice that when we declared the ArrayList we didn't give it a size. Then we were able to ask the ArrayList for its size, we were able to ask it whether it contained specific objects, we removed an object right out from the middle of it, and then we rechecked its size.

Answer 5

The java.util.ArrayList class is one of the most commonly used of all the classes in the Collections Framework. Some of the advantages ArrayList has over arrays are

• It can grow dynamically.

• It provides more powerful insertion and search mechanisms than arrays.

Let's take a look at using an ArrayList that contains Strings. A key design goal of the Collections Framework was to provide rich functionality at the level of the main interfaces: List, Set, and Map. In practice, you'll typically want to instantiate an ArrayList polymorphically like this:

List myFirstArrayList = new ArrayList();

As of Java 5 you'll want to say

List myFirstArrayList = new ArrayList();

This kind of declaration follows the object oriented programming principle of "coding to an interface", and it makes use of generics. We'll say lots more about generics in future, but for now just know that, as of Java 5, the syntax is the way that you declare a collection's type. (Prior to Java 5 there was no way to specify the type of a collection, and when we cover generics, we'll talk about the implications of mixing Java 5 (typed) and pre-Java 5 (untyped) collections.)

In many ways, ArrayList is similar to a String[] in that it declares a container that can hold only Strings, but it's more powerful than a String[]. Let's look at some of the capabilities that an ArrayList has

List test = new ArrayList();

String s = "hi";

test.add("string");

test.add(s);

test.add(s+s);

System.out.println(test.size());

System.out.println(test.contains(42));

System.out.println(test.contains("hihi"));

test.remove("hi");

System.out.println(test.size());

which produces

3

false

true

2

There's lots going on in this small program. Notice that when we declared the ArrayList we didn't give it a size. Then we were able to ask the ArrayList for its size, we were able to ask it whether it contained specific objects, we removed an object right out from the middle of it, and then we rechecked its size

Answer 6

The java.util.ArrayList class is one of the most commonly used of all the classes in the Collections Framework. Some of the advantages ArrayList has over arrays are

Answer 7

An Arraylist is used to store data and contains methods to help the programmer access and store data in an Arraylist. It has the ability to expand its size and make more room for more data.