Primitive Data Types
All these types are passed by values and initialized to
null, Whether they are class's member or method variable. Make sure you initialize to appropriate value before using them.
Boolean flag = true;
Integer i = 2;
Double d = 3.14159;
Decimal n = d or n = i; //This type include decimal point
Long l = 2147483648L;
Object obj = 10;
Integer i = (Integer)obj;
MyApexClass o = (MyApexClass)obj;
o.myMethod();
String s = 'Hello World';
ID accountId = '001XXXXXXXXXXXXXXX';
sObject Types
Any object can be stored in salesforce database.
An sObject represents a row of data.
Account a = new Account(Name = 'Test', ...);
MyCustomObject__c cusObj = new MyCustomObject__c(Name = 'Test', ...);
sObject sObj = new Account();
Account acc = (Account)sObj;
User Defined Types
Refers to classes and interfaces in apex
MyApexClass obj = new MyApexClas();
MyApexInterface obj = new MyApexClassImplemented();
Collection Types:
Lists
A list is an order of collection elements that are distinguished by their indices. List element can be of any data types - primitive data types, collections, sObjects, user-defined types and built-in Apex types. For example:
To declare a list, use the List keyword followed by the primitive data, sObject, nested list, map of set type within <> characters. For example:
// Create an empty list of String
List<String> my_list = new List<String>; //or new String[0];
// Create an empty list of Account
Account[] accs = new Account[0];
List<Account> lAcc = new List<Account>();
//Create an empty list of user-defined type
List<MyApexClass> myApexs = new List<MyApexClass>();
//Create nested list
List<List<List<Integer>>> nestedList= new List<List<List<Integer>>>();
To access element in list, use the list methods provided by Apex. For example:
my_list.add('Red');
my_list.add('Orange');
System.assertEquals('Orange', my_list.get(1));
You can populate list elements when the list is declared by using curly brace ({})
List<String> lst = new List<String> {'Red','Orange', ...};
System.assertEquals('Red', lst [0]);
System.assertEquals('Orange', lst.get(1));
List<Account> accounts=[select id,name from Account];
You can create new instance of the List class by copying the elements from specific list.
List<String> my_list1 = new List<String>{'Red','Orange'};
List<String> my_list2 = new List<String>(my_list1 );
You can create new instance of the List class by copying the elements from specific set.
Set<Integer> setInts = new Set<Integer>{1,2,3};
List<Integer> myIntegers= new List<Integer>(setInts);
Sets
A set is an unordered collection of elements that do not contain any duplicates. Set elements can be of any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types. For example, the following table represents a set of strings, that uses city names:
'San Francisco', 'New York' 'Paris' 'Tokyo'
Sets can contain collections that can be nested within one another. For example, you can have a set of lists of sets of Integers. A set can contain up to four levels of nested collections inside it, that is, up to five levels overall.
To declare a set, use the Set keyword followed by the primitive data type name within <> characters. For example:
Set<String> mySet = new Set<String>();
You can populate elements when the set is declared by using curly brace ({})
Set<String> sets = new Set<String>{'Red','Orange', 'Banana'};
Creates a new instance of the Set class by copying the elements of the specified set
Set<String> setsx= new Set<String>(sets);
To access elements in a set, use the system methods provided by Apex. For example:
Set<String> s= new Set<String>();
s.add('Apple');
System.assert(s.contains('Apple'));
s.remove('Apple');
System.assert(s.size()==0);
Creates a new instance of the Set class by coping the list elements
List<String> ls = new List<String>();
ls.add('Apple');
ls.add( 'Orange');
ls.add('Apple');
Set<String> sets =new Set<String>(ls);
System.assert(sets.size()==2);
Maps
A map is collection of key-value pairswhere each unique key maps to single value. Keys and values can be any data type - primitive data types, collections, sObjects, user-defined types and built-in Apex types. For example:
Country(key) - 'United States', 'Japan', 'France',...
Currency(value) - 'Dollar', 'Yen', 'Euro',...
To declare a map, use the Map keyword followed by the data type of the key and the value within <> characters. For example:
//Map of primitive data type String
Map<String,String> country_currency = new Map<String,String>();
//Map of Account
Map<ID, Account> idAccount =new Map<ID, Account>();
//Map of sObject type, see bellow
Map<ID, sObject> idsObject = new Map<ID, sObject>(List<sObject>);
//Map of collection type Set
Map<String,Set<String>> mapCollection = new Map<String,Set<String>>();
//Map of user-defined type MyApexClass
Map<String,MyApexClass> mMyApex = new Map<String,MyApexClass>();
To access elements in a map, use the map methods provided by Apex. For example:
country_currency .put('United States', 'Dollar');
country_currency .put( 'Japan', 'Yen');
System.assertEquals(true, country_currency.containsKey('Japan'));
System.assertEquals('Yen', country_currency.get('Japan'));
You can populate map key-value pairs when the map is declared by using curly brace ({})
Map<String,String> mString= new Map<String,String>{'a' => 'Apple', 'b'='Book'};
The value for key a is Apple and b is Book.
You can create new instance of the Map class and populate it with passed-in list of sObject records. The keys are sObject IDs and the values are sObjects
List<Account> ls= [select Id,Name from Account];
Map<ID, Account> idAccountRecords = new Map<ID, Account>(ls);
