What Is a Map In Apex?

Map:

         A map is a collection of key-value pair values. Keys can be any primitive data type, while values can be a primitive, sObject, collection type or an Apex object. Keys have to be unique in the collection where as values can be duplicate.

Also Read: What Is Collections In Apex?

The following table represents a map of Employee Id’s and Employee Names

121	127	657	985	111	123
‘Nagarjun’	‘Hari’	‘Krishna’	‘Praveen’	‘Mahi’	‘Malli’

Map Syntax:

// Declaring Map
Map<Keydatatype,Valuedatatype> mapname;

// Creating a new map
Map<Keydatatype,Valuedatatype> mapname = New Map<Keydatatype,Valuedatatype>();

Map Methods
PUT Method: Adds pairs to the map or associates value to a specific key in a map.

// Add to map 
Map<Integer, String> Empmap = Map<Integer,String>();
Empmap.put(121,'Hari');
Empmap.put(122,'Krishna');

// Add s-Object wiht id to Map
Map<Id, Account> Accmap = Map<Id,Account>();
Empmap.put(acc1id,acc1);
Empmap.put(acc2id,acc2);

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Get Method: Allows us to retrieve keyvalues from a map using the key.

// Get Elements from map
Map<Integer, String> Empmap = Map<Integer,String>();
Empmap.put(121,'Hari');
Empmap.put(122,'Krishna');
String s = Empmap.get('121') 
String s = Empmap.get('122')

Remove Method: Retrieves element from a Map.

// Remove Element From Map
Map<Integer, String> Empmap = Map<Integer,String>();
Empmap.put(121,'Hari');
Empmap.put(122,'Krishna');
Empmap.remove(121);

Clear Method: Removes all the elements from the Map and sets the size of the Set to Zero.

// clear the Elements From Map
Map<Integer, String> Empmap = Map<Integer,String>();
Empmap.put(121,'Hari');
Empmap.put(122,'Krishna');
Empmap.clear();

Clone Method: Creates a new Map and adds all the elements of an existing Map into that new Map.

// Cloning the map
Map<Id,Account> Accmap = New Map<Id,Account>();
Accmap.put(id1,'Hari');
Accmap.put(id2,'Krishna');
Map<Id, Account> map2 = Emp1map.clone();

Note: If this is a map with sObject record values, the duplicate map will only be a shallow copy of the map. That is, the duplicate will have references to each sObject record, but the records themselves are not duplicated.

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Deepclone Method: Creates a new Map and adds all the elements of an existing Map physically into that new Map.

// Example 1
Map<Id,Account> Accmap = New Map<Id,Account>();
Accmap.put(id1,'Hari');
Accmap.put(id2,'Krishna');
Map<Id, Account> map2 = Emp1map.clone(); 

//Example 2
Map<Integer,Account> Accmap = New Map< Integer,Account>();
Accmap.put(121,'Hari');
Accmap.put(122,'Krishna');
Map<Id, Account> map2 = Emp1map.cloneclone();

ContainsKey Method: Boolean method which helps us to check if a key is present in a map.

// Check the Elements in Map
Map<Integer,Account> Accmap = New Map< Integer,Account>();
Accmap.put(121,'Hari');
Accmap.put(122,'Krishna');
Boolean contains = Accmap.containsKey(121);

IsEmpty Method: Boolean method which returns true if the Map has no elements.

// Check the Map empty
Map<Integer,Account> Accmap = New Map< Integer,Account>();
Accmap.put(121,'Hari');
Boolean isitempty = Accmap.isEmpty();
system.debug('The map is Empty' + isitempty);
Result:- 13:32:49:023 USER_DEBUG [3]|DEBUG|The map is Empty False

Size Method: Return the number of the elements stored in the Set.

// Check the Size of the Map
Map<Integer,Account> Accmap = New Map< Integer,Account>();
Accmap.put(121,'Hari');
Accmap.put(122,'Krishna');
Integer accmapsize = Accmap.Size();
system.debug('The map size is' + accmapsize);
Result:- 13:32:49:023 USER_DEBUG [3]|DEBUG|The map size is 2

keySet Method: Returns a set or list that contains all of the keys in the map.

// Set the key to Map
Map<Integer,Account> Accmap = New Map< Integer,Account>();
Accmap.put(121,'Hari');
Accmap.put(122,'Krishna');
Set<Integer> acctnums = Accmap.keySet();

Values Method: Returns a list that contains all of the values in the map in the arbitrary order.

// Return the map values 
Map<Integer,Name> Empmap = New Map< Integer,Account>();
Empmap.put(121,'hari');
Empmap.put(122,'Krishna');
List<String> Empnames = Empmap.values();