Difference between arraylist and array

Answer 1

Terms from computer science:

You can imagine list like as string of pearls. They are connected with thread. If you got one you can go by thread to the other one next to it.

An array is like a meter. You know where you are so you can jump any amount of units around.

Answer 2

I am assuming that you are talking about Linked List and Arrays, Linked list are made up of nodes, which reference data and another node. Arrays on the other hand are just simply blocks in the memory to hold sequential data.

Thus Arrays require contiguous memory (the memory allocated must be together, and increasing this allocation may need a new location, since new data may overflow to pre-existing data), while Linked Lists do not.

Since Linked Lists are "linked" sequentially, there is no support for random access (all access must be traversals from the front to the desired value).

Arrays are more efficient for data structures that are rarely modify (thus getting around the contiguous memory requirement), and Linked List allow efficient modification (all adds and removes are constant efficiency, while arrays must shift elements).

Answer 3

A "collection" is a type of object that holds related data objects. Depending on the language you are using, collections might include hash tables, dictionaries, vectors, arrays, lists, sets, maps, stacks, queues, or any other type of object whose purpose is to contain sets of data that can be iterated or accessed in a variety of ways. An array is a specific type of collection that is of fixed size, and provides access to records through indices.

Answer 4

in Arraylist - will face issues Like Boxing and unboxing But in List (Generics) No boxing and Unboxing so that generics are type safety example : private void button1_Click

(object sender, EventArgs e)

{

//Arraylist - Arraylist accept values as object

//So i can give any type of data in to that.

//Here in this eg: an arraylist object accepting

//values like String,int,decimal, char and a custom object

Employee emp = new Employee("2", "Litson");

ArrayList arr = new ArrayList();

arr.Add("Sabu");

arr.Add(234);

arr.Add(45.236);

arr.Add(emp);

arr.Add('s');

//This process is known as boxing

//To get inserted vales from arraylist we have to specify the index.

//So it will return that values as object.

//we have to cast that value from object to its original type.

String name = (String)arr[0];

int num = (int)arr[1];

decimal dec = (decimal)arr[2];

Employee em = (Employee)arr[3];

char c = (char)arr[4];

//This process that is converting from object to its original type is known as unboxing

//------------------------------------------------------------------------------------

//Generic List

//List<>

//Main advantage of Generic List is we can specify the type of data we are going to insert in to

//List. So that we can avoid boxing and unboxing

//Eg:

List<String> strLst = new List<string>();

strLst.Add("Sabu");//Here List accepting values as String only

strLst.Add("Litson");

strLst.Add("Sabu");

strLst.Add("Sabu");

List<int> intLst = new List<int>();

intLst.Add(12);//Here List accepting values as int only

intLst.Add(14);

intLst.Add(89);

intLst.Add(34);

List<decimal> decLst = new List<decimal>();

decLst.Add(2.5M);//Here List accepting values as deciaml only

decLst.Add(14.4587m);

decLst.Add(89.258m);

decLst.Add(34.159m);

List<Employee> empLst = new List<Employee>();

empLst.Add(new Employee("1", "Sabu"));//Here List accepting Employee Objects only

empLst.Add(new Employee("2", "Mahesh"));

empLst.Add(new Employee("3", "Sajith"));

empLst.Add(new Employee("4", "Binu"));

//To get values from Generic List

String nme = strLst[0]; //No need of casting

int nm = intLst[0];

Decimal decVal = decLst[0];

Employee empVal = empLst[0];

}

Thanks khiroj kumar sahu (khiroj.kumarsahu@photoninfotech.net)

Answer 5

An array list contains primitive types, while an ArrayList contains objects. However, this does not mean that an ArrayList cannot hold integers. In fact, through auto-boxing, int are automatically converted into Integers before put into ArrayList.

Another difference is that an array has a fixed number of items in it, while an ArrayList can grow or shrink.

An ArrayList has its own methods from import java.util.ArrayList. For example, to retrieve an object in a certain location, you would use get(i). However, for an array you would have to access array[i].

Another difference is how you initialize it:

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

compared to

String[] theList = new String[i];

There are many difference, but ultimately, it is up to you to decide which one is easier to work with.

Answer 6

In VB.net, an Array has a defined count, whereas an ArrayList can be populated dynamically. You can perform advanced calculations on an Array, making it more powerful, but it is much easier to populate an ArrayList. For example:

For i as integer = 0 to 100

ReDim Preserve myArray(i)

myArray(i) = i

Next

For i as Integer = 0 to 100

myArrayList(i) = i

Next

Answer 7

An array list is a collection of one or more (usually more) elements arranged in memory in a consecutive fashion, accessed as one indexable entity. The upside is that overhead is small. The downside is that size is fixed, unless you implement some method of size extension, copying, deleting, etc.

A linked list is a collection of one or more (usually more) elements arranged in memory in a (usually) dis-contiguous fashion, using pointers contained in each element that point to the next element in the list. Each element is allocated one at a time (although some algorithms can allocate chunks, in order to optimize things). The upside is that the list is growable to the limit of available memory. The downside is that there is overhead, both in element size and in addition, deletion, and searching.

Answer 8

Arraylist provide a lot of functionalities over array .Array have fixed size and can not increase dynamically if there is need during of execution . But in case of arraylist it can increase their size if needed .So we can say array is fixed in size and arraylist is dynamic or re sizable array .Second , arraylist provide a lot of predefined method for different functionalities so it make developer work easy because these method well efficient.