Collections in Salesforce - A Brief Guide

Collections could be a sort of variable that can store numerous records. For case, List can store numerous Account object's records. Let us presently have a point-by-point diagram of all collection sorts.

List

A list is an ordered collection of elements that are distinguished by their indices. List elements can be of any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types. Lists can contain any collection and can be nested within one another and become multidimensional.

Example:

List<string> ListOfCities = new List<string>();
System.debug('Value Of ListOfCities'+ListOfCities);

Methods for Lists:

There are strategies accessible for Records that are ready to be utilized whereas programming to attain a few functionalities like calculating the estimate of List, including a component, etc. Following are a few most regularly utilized strategies −

• size()
• add()
• get()
• clear()
• set()

You'll be able to utilize the cluster documentation as well to pronounce the List, as given underneath, but usually not common hone in Pinnacle programming− 

String [] ListOfStates = new List<string>();

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Sets

A Set is a collection type that contains multiple numbers of unordered unique records. A Set cannot have duplicate records. Like Lists, Sets can be nested.

Example:

Set<string> ProductSet = new Set<string>{'Phenol', 'Benzene', 'H2SO4'};
System.debug('Value of ProductSet'+ProductSet);

Methods for Sets:

Set<string> ProductSet = new Set<string>{'Phenol', 'Benzene', 'H2SO4'};
ProductSet.add('HCL');
System.debug('Set with New Value '+ProductSet);

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Maps

It may be a key esteem combine that contains a one-of-a-kind key for each esteem. Both key and esteem can be of any information sort.

Example:

Map<string, string> ProductCodeToProductName = new Map<string, string>
{'1000'=>'HCL', '1001'=>'H2SO4'};