• Lists
    A list is an ordered collection of elements that are distinguished by their indices. List elements can be of any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types.
  • 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.
  • Maps
    A map is a collection of key-value pairs where each unique key maps to a single value. Keys and values can be any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types.

 

List – An ordered collection of Similar Data types. Every element in a list will be identified by a unique index. It allows duplicates

Index 0 1 2 3 4
Value Red Blue Orange White Green

List<data type>  variable;

List&lt;String&gt;strList;
strList=new List &lt;String&gt;();

// Alternate way

List &lt;String&gt; colors=new list&lt;String&gt;();
colors.add('Red');
colors.add('Blue');
colors.add('Green');
System.debug('Colors added'+colors);

Output: Colors added(Red, Blue, Green)

List allows duplicate values

List &lt;String&gt; colors=new list&lt;String&gt;();
colors.add('Red');
colors.add('Blue');
colors.add('Green');
colors.add('Red');
System.debug('Colors added'+colors);

Output: Colors added(Red, Blue, Green,Red)

// Alternate way



List&lt;String&gt; colors=new List&lt;String&gt;{'Red','Green','Blue'};


Retrieve the color from that position…




Salesforce assigns index values to the list values automatically.
List is a ordered collection.


Colors.get(2);
Colors.get(1);
String colour=colors.get(1);
System.debug('Element in 2nd position'+colour);
System.debug('Element in 1st position'+colors.get(0));
System.debug('Element in 3rd position'+colors.get(2));



How to find the size of the LIST?

ANS: Colors.size();


integer size=colors.size();
System.debug('Size of the list'+size);



Clears the elements from the list


colors.clear();
System.debug('Elements in the list now'+colors);


List is a ordered collection, similar data type and allows duplicates


List&lt;Account&gt; accList=new List&lt;Account&gt;();
Account a1=new Account();
a1.name='AxisBank';

Account a2=new Account();
a2.name='CitiBank';

Account a3=new Account();
a3.name='HDFCBank';
accList.add(a1);
accList.add(a2);
accList.add(a3);
insert accList;
System.debug('Elements in the List'+accList);


Using a single DML, a collection of records is inserted.

Error: Too Many DMLS 151 (If we cross the governor limit of 150 DML statements)

Whenever we point to a lookup field..go for ID


Custom Object


List <Employee__c> empList=new List<Employee__c>();
Employee__c e1=new Employee__c(Name='Mark',Position_set__c='a0B6F00001QKlIx');
empList.add(e1);
Employee__c e2=new Employee__c(Name='Tom',Position_set__c='a0B6F00001QKlIx');
empList.add(e2);

insert empList;
System.debug('First Account'+accList[0]);


we can use like above instead of get.

Retrieving the values: SOQL – Salesforce Query Language should be inside [ ]


List<Account> accList=new List<Account>();
accList=[Select id,name from Account];
System.debug('Account List'+accList);

List<Account> accList=new List<Account>();
accList=[Select id,name from Account];
Account a=[Select id,name,AccountNumber,Rating from Account limit 1];
System.debug('Account List'+accList);
System.debug('Account details'+a);
System.debug('Account name'+a.Name);
System.debug('Account number'+a.AccountNumber);
System.debug('Account Rating'+a.Rating);</pre>




All the fields that are shown in output must be retrieved in SOQL first or else

the error will be thrown.


Account a=new Account(Name='Amazon web services');
insert a;

Contact c=new Contact();
c.LastName='Tst';
c.Accountid=a.id;
insert c;



SET


    

  • An unordered collection of similar data types
    • 

  • Set Does not allow duplicate elements.
    • 



Systax


Set<DATATYPE> variable;


Set<String> colorSet= new Set<String>();


SETS: doesnot allow duplicates, unordered collection, with similar data types


Set<data-type> variable=new Set<data-type>();


Set<String> Colorset=new Set<String>();
colorset.add('red');
colorset.add('blue');
colorset.add('green');
colorset.add('red');

System.debug('Elements in the List'+colorSet);




Output:Elements in the Set{blue, green, red}


Whenever we have to store ID’s we go for set (no dup).


clear

size allowed

get method not supported


 


MAP


MAPS: 



Map<key, value> variable=new Map<key, value>();


key and value are data types

Each value is identified by a key. values can be duplicate but key should be unique


Map<integer,String> StrMap=new Map<integer,String>();
StrMap.put(1,'Red');
StrMap.put(10,'Green');
StrMap.put(50,'Blue');
StrMap.put(50,'Amber');
StrMap.put(250,'Green');

System.debug('Colors in the Map'+StrMap);



Output: Colors in the Map{1=Red, 10=Green, 50=Amber, 250=Green}


Map.values -To map the values (List of values)

Map.keyset (set of keys)


System.debug('List of colors is'+StrMap.values());

System.debug('Keys in the map'+StrMap.keySet());


System.debug('Color for code 50 is'+strMap.get(50));

System.debug('Color for code 150 is'+strMap.get(150));


List <String> fruits=new List<String>{'apple','orange','pineapple','jack'};
Iterator<String> itr=fruits.iterator();
while(itr.hasnext()){
System.debug('third fruit'+itr.next());
}
for(String s:fruits)
{
   System.debug('fruit'+s) ;
}




Set <String> flowers=new Set<String>();
flowers.add('rose');
flowers.add('lilly');
flowers.add('jasmine');
System.debug('flowers'+flowers);
for(String q:flowers)
{
    System.debug('loop flowers'+q);
}
Iterator<String> w=flowers.Iterator();
while(w.hasnext())
{
    System.debug('flowers'+w.next());
}