Collection | List

List: A List can hold any type of data and is one of the most important types of collection. A list is an ordered collection of any data type such as primitive types, collections, sObjects, user-defined types, and built-in Apex types.

The Following are the key features of a list collection in salesforce:

·      Duplicates and nulls are allowed in a list collection.

·      “List” is the keyword to declare a list collection.

·      In a list collection, the index position of the first entry is always zero (0).

·      An Apex list collection has the ability to grow dynamically over time.

·      In a list collection, the data type can be both primitive and non-primitive.

·      The keyword followed by the data type has to be used within <> characters to define a list collection.

 

The syntax for a list is as follows:

List<datatype> listName = new List<datatype>();

 

List Class Salesforce: All Methods required for a list collection are stored in the Apex list class.

 

What are the Methods in List?

 In order to use lists in programming to achieve certain functions, a few methods in salesforce are available.

 

The following are the list-class methods in salesforce:

§  Add

§  Clone

§  Remove

§  Size

§  Equals

§  Get

§  Set

§  Clear

        Add: The Values or items are added to the list using the list.add() method.

Syntax:

List name.add ();

Example:

List <String> names = new List<String>();

names.add(‘Sfdc’);

Clone: It is the method of making a new record by sing the details of an existent one. Simply put, it is creating a duplicate record.

Syntax:

NewList = Old list name. clone ();

Example:

New Names = names. Clone ();

Remove: It is the method of removing the specific value of the list.

Syntax:

List Name.remove(index);

Example:

List<String> names = new List<String>();

names.add(‘Sfdc’);

names.add(‘Telugu’);

names.add(‘Salesforce’);

names. remove (2);

Size: It is the method of finding the number of elements present in the list.

Syntax:

Listname.size();

Equals: This is the method of defining whether the value is equal or not. If the list and the specific list are equal, true is returned; otherwise, false is returned.

Syntax:

result=Listone.equals(Listtwo);

Here, “List two” is being compared with “Listone”. If both elements are the same, it shows true; if both elements are not the same, then it shows false.

Get: This is the method that helps to return or find out a value from a list.

Syntax:

String getlist = list.get(index);

In this syntax, you have to replace “list” with “list name” and “index” with “index number”.

 

Set: This is the method that is used to change the element or value of an index.

Syntax:

List.set (index, value);

The value of the index, which is mentioned in the code, will be changed to the value that is present in the code.

 

Example:

If you write names.set (1, Mark);

Here the value at the “index1” of the list of “names” will be changed to “mark”.

Clear: This is the method that removes or deletes an element in the list.

Syntax:

list. clear ();

 

Set Collection

Set is an unordered collection. It is a unique set of values that do not have any duplicates. If you want no duplicates in your collection, then you should opt for this collection.

·       A set collection dose not have an index.

·       A set collection does not contain any duplicates or null values.

·       Any data types, such as primitive data types and sObjects, are allowed in a set collection.

·       Set collections are not widely used in salesforce Apex.

·       Sets can hold collections that are nested inside of one another.

·       You have to use the set keyword followed by the primitive data type name within <> characters to declare a set collection.

Syntax:

Set<datatype> setName = new Set<datatype>();