Salesforce Collection

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What is a collection?

A group of elements or similar types of elements is called collection.

There are three types of Salesforce Collection:-

  1. Map
  2. Set
  3. List
Map: Map is key-value pairs.

Syntax: 
Map<Key,Value> nameOfMap = new Map<Key,Value>();

Key → is a set. 

Value or Values → is a list. 

Methods in Map:
  • put()      → add a key-value pairs.
  • get()      → retrieve a value for a key.
  • keySet() → retrieve all the keys and return type is set.
  • values() → retrieve all the values and return type is list.
  • size()     → return the number of components in the map.

Set: Set is an ordered collection of elements which will not allow duplicate.

Syntax:
Set<Type> NameOfSet = new Set<Type>();

Type → String or Integer or any data type.

Methods in Set:
  • add() → to add.
  • get() → to get value by index.

List: List is an unordered collection of elements which will allow duplicate.

Syntax:
List<Type> NameOfList = new List<Type>();

Type → String or Integer or any data type.


Methods in List:
  • add()      → add the values to the list.
  • get()      → retrieve a value from a list using the index.
  • set()      → replaces a former value with the value at given index.
  • clear()   → Remove the elements from the list.
  • size()     → return the number of elements in the list.

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