DIFFERENCE BETWEEN SET, LIST AND MAP

Three different types of collections in Apex.

1. List
2. Set
3. Map

• List: List simply called collection of duplicate values and which contains Integer indexed data.

• Create new LIST.
• List<String> myList = new List<String>();

• Add into LIST.
• myList.add(‘Navin’);
• myList = new List<String>{ ‘Navin’, ‘Aryan’ };

• Duplicate means?
• myList.add(‘Navin’);
• myList.add(‘Aryan’);
• myList.add(‘Navin’);
• Here the size of LIST is 3. We can get this by myList .size()
• At index 0, myList[0] = we get Navin
• At index 1, myList[1] = we get Aryan
• At index 2, myList[2] = we get Navin

• Set: Set simply called collection of Unique values and cannot be sort.

• Create new SET.
• Set<String> mySet = new Set<String>();

• Add into Set.
• mySet .add(‘Navin’);
• mySet = new mySet <String>{ ‘Navin’, ‘Aryan’ };

• Unique means?
• mySet.add(‘Navin’);
• mySet.add(‘Aryan’);
• mySet.add(‘Navin’);
• Here the size of SET is 2. We can get this by mySet .size()
• We can check “if(mySet .contains(‘Navin’)){ system.debug(‘mySet=>’+ mySet.size())}”. Which shows answer is “mySet=>2″

• Map: Maps are collections of key-value pairs, where the keys is Unique.

• Create new Map.
• Map<Integer,String> employeeAddresses = new Map<Integer,String>();
• Integer is KEY and it is unique.
• String is VALUE.
• Example : School Bag(Unique) with same and different book and copy(Not Unique).

• Add into Map.
• employeeAddresses.put (1, ‘123 Sunny Drive, San Francisco, CA’)

•  Unique means?
• employeeAddresses.put (1, ‘456 Dark Drive, San Francisco, CA’);
• employeeAddresses.put (2, ‘456 Dark Drive, San Francisco, CA’);
• employeeAddresses.put (1, ‘222 White Drive, San Francisco, CA’);
• Here the size of MAP is 2. We can get this by employeeAddresses.size()
• We can check “if(employeeAddresses .containsKey(‘1′)){ system.debug(’employeeAddresses =>’+ employeeAddresses .get(‘1’))}”. Which shows answer is “employeeAddresses =>222 White Drive, San Francisco, CA”
• Here we can see 1 that is key and can override with last value i.e. “222 White Drive, San Francisco, CA” not “456 Dark Drive, San Francisco, CA”.