Salesforce Apex Map & Map methods with Examples

Map is one of the collection type in salesforce apex. In this post we are going to see what are the map methods with some basic examples. First of all Map is a key and value pair i.e each and every value is associates with key. Here key is unique, that means if we put one key,value pair into Map, we should not add same key one more time. If key is already exist in map and once again you are trying to add key with different value then old value override with new value.

Salesforce Apex Map Syntax:

Map<dataType, dataType> variabeName ;

If we don't initialize map and 'trying to put new set of key, value' Or trying to use any map methods on that variable, you will end up with null pointer exception. So we need to initialize map whenever we create map variable.

Map<dataType, dataType> variabeName = new Map<dataType, dataType>();

eg: Map<String, String> countryWithCapitalMap =  new Map<String, String>();

Important Apex Map Methods:

put( ): By using this method we can new set of key, value pair into map.

example: countryWithCapitalMap.put('India', 'Delhi'); //here India is key & Delhi is corresponding value for key 'India'.

containsKey(key): By using this method we can check whether key exist or not in Map. It will return true if key is exist in apex map.

example: countryWithCapitalMap.containsKey('India') //true

get(Key): It returns value of corresponding key.

example:  countryWithCapitalMap.get('India') //reurns 'Delhi'

isEmpty(): It returns true if Map does not contain any key, value pair.
example:  countryWithCapitalMap.isEmpty() //false

size():  It returns number of key, value pairs available in Map.

example: countryWithCapitalMap.size() // 1

keySet(): It returns SET of key's available in the map.

example: countryWithCapitalMap.keySet() //{India}

values(): It returns LIST of values available in map.
example: countryWithCapitalMap.values() //{Delhi}

Task: Create a map to store country as Key and corresponding countries as values.

Country (Key)	'United States'	'India'
States (Value)	'California', 'Colorado',  'Texas'	'Andhra Prdesh', 'Telangana', 'Karnataka'

One country can have multiple states so that we should create Map value as List<string>

Map<String, List<String>> countryWithStatesMap = new Map<String, List<String>>();

countryWithStatesMap.put('United States', new List<String>{'California','Colorado','Texas'});
countryWithStatesMap.put('India', new List<String>{'Andhra Prdesh','Telangana','Karnataka'});

system.debug('Get countries from countryWithStatesMap ===>'+countryWithStatesMap.keyset());
// o/p: {India, United States}
system.debug('Get States of India ===>'+countryWithStatesMap.get('India'));

// o/p: (Andhra Prdesh, Telangana, Karnataka)

system.debug('Is Srilanka there in Map ===>'+countryWithStatesMap.containsKey('Srilanka')); 

// o/p: false

Subjects:

Apex Apex Collections Development Salesforce Apex Triggers Salesforce Development Real-time Interview Questions

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