What Is a SET In Apex?

Set:

              A set is an unordered collection of typed primitives, sObjects. For example, the following table is a visual representation of a set of Strings. But Sets do not allow duplicate values to be stored in them.

Also Read: What Is Collections In Apex?

Set Syntax:

                  To declare a set, use the Set keyword followed by the primitive data, sObject type within "<  >" characters.

// Declaring Set
Set<datatype> setname;

//Declaring Set of String
Set<string> nameset;

//Creating an empty set of strings
Set<String> my_set = new Set<String>();

Set Methods:
ADD Method: Adds elements to a Set.

// add single ingeger to Set
Set<Integer> numSet = new Set<Integer>();
numSet.add(23);
// (OR) Add multiple elements to Set
Set<Integer> numSet = new Set<Integer>(30,20,1);

// Add strings to Set
Set<String> nameSet = new Set<String>();
nameSet.add('ramesh');
nameSet.add('Sreenu');
nameSet.add('Hari');

// Add S-objects to Set
Set<Account> accSet = new Set<Account>();
Account acc = New Account();
Acc.name = ' Nagarjun';
accSet.add(acc);

You May Also Like: What Is a Map In Apex?

CONTAINS Method: Allows us to check if an element is present in a Set or not.

Set<Integer> numSet = new Set<Integer>();
numSet.add(23);
Integer Mynum = numSet.get(0); //Retrieves first occurrence from the numSet. 

Set<String> nameSet = new Set<String>{'Nagarjun','Malli','Hari');
Boolean Result;
result = myString.contains('Malli');
system.assertEquals(result, false);

Remove Method: Retrieves element from a Set.

// Remove Integers Elements from Set
Set<Integer> numSet = new Set<Integer>(20,10,30);
numSet.remove(20);  // Removes 20 from the numSet. 

// Remove Strings Elements from Set
Set<String> nameSet = new Set<String>('Nagarjun','Malli','Hari');
NameSet.remove('Hari')  //Removes 'Hari' from the nameSet.

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

// Clear the elements from Set
Set<Integer> numSet = new Set<Integer>(20,10,30);
numSet.clear(); // Removes all elements from the numSet. 

Set<String> nameSet = new Set<String>('Nagarjun','Malli','Hari');
NameSet.clear() //Removes all names from the nameSet.

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

// Clone the numset to newnumset
Set<Integer> numSet = new Set<Integer>(20,10,30);
Set<Integer> newnumset = numset.clone(); //Creates a duplicate copy all elements from the numSet into newnumset. 

// Clone Strings from nameset to newnam
Set<String> nameSet = new Set<String>('Nagarjun','Malli','Hari');
Set<Integer> newnameSet = nameset.clone(); //Creates a duplicate copy all elements from the nameSet into newnameset.

// Clone s-Object 
Set<Account> accSet = new Set<Account>(a1,a2,a3);
Set<Account> newaccSet = accSet.clone() //Creates a new Set newaccSet and virtually creates the new elements a1,a2,a3 into it.

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

// Empty the Set
Set<String> nameSet = new Set<String>{'Nagarjun','Malli','Hari'};
nameSet.clear();  //all the elements are now removed from the nameSet using the clear method, the nameSet will now be empty and hence isempty method will return true. 

system.debug('The name Set is ' + nameSet.isempty());
Result:- 13:32:49:023 USER_DEBUG [3]|DEBUG|The name Set is true

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

//  Find the Set size
Set<String> nameSet = new Set<String>{'Nagarjun','Malli','Hari'}; 
Integer I = nameSet.size(); // the nameSet size is 3

system.debug('Number of elements in nameSet are' + nameSet.size());
Result:- 13:32:49:023 USER_DEBUG [3]|DEBUG| Number of elements in nameSet are 3