Map In salesforce

The Map methods are all instance methods, that is, they operate on a particular instance of a map. The following are the instance methods for maps What is map?

• A map is a collection of key-value pairs where each unique key maps to a single value. In map Keys can be any primitive data type like string, integer,decimal, Id while values can be a primitive, sObject, collection type or an Apex object.
• Map keys and values can be of any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types.
• Map keys of type String are case-sensitive. Map methods, including put, get, containsKey, and remove treat these keys as distinct.
• Map gives value on basis of key.
• Key always unique but value can be duplicated.

Syntax

Map<integer, string>exMap= new map<integer, string>();
exMap.put(1,'James');
exMap.put(2,'Daniel');
exMap.put(3,'Peter');
string name= exMap.get(1);
string name1= exMap.get(2);
string name2= exMap.get(3);
system.debug(name);//James
system.debug(name1);//Daniel
system.debug(name2);// Peter
set<integer>key= exmap.keyset();
list<string>values=exmap.values();
system.debug(values);//James, Daniel, Peter

Map Methods

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The following are methods for Map. All are instance methods.

• clear() Removes all of the key-value mappings from the map.
• clone() Makes a duplicate copy of the map.
• containsKey(key) This method returns true if the map contains  the  If the key is a string, the key value is case-sensitive.
• deepClone() DeepClone () method creates a duplicate copy of a map, including sObject records if the map has sObject record values .
• equals(map2) It compares a map with a specified map and returns true if both maps are equal; otherwise, returns false.
• get(key) This method returns the value of the specified key which is mapped, or it returns null if the map contains no value for this key.
• getSObjectType() This method returns the value of the sObject type in format of key and value.
• isEmpty() If map has zero key-value pairs it returns true.
• keySet() Returns a set that contains all of the keys in the map.
• put(key, value):
• Associates the specified value with the specified key in the map.
• putAll(fromMap) Copies all of the mappings from the specified map to the original map.
• putAll(sobjectArray) Adds the list of sObject records to a map declared as Map<ID, sObject> or Map<String, sObject>.
• remove(key) This method removes the mapping for the specified key from the map, if present, and returns the corresponding value.
• size() Returns the number of key-value pairs in the map.
• values() This methods returns a list which contains all the values in the map.The values are returned in an arbitrary order.

get(key):

list<account>myAccounts = new list<account>();
myAccounts = [Select ID, Name from Account limit 10]; 
map<id,string>myAMap = new map<id,string>();
for ( Account a : myAccounts ){
//Here putting account Id and name to map
myAMap.put(a.ID, a.Name);
    } 
for ( ID aID : myAMap.keySet() ){
system.debug(loggingLevel.debug, myAMap.get(aID));
    }    

putAll(fromMap):

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Map<String, String> map1 = new Map<String, String>();
map1.put('Red','LightRed');
Map<String, String> map2 = new Map<String, String>();
map2.put('Blue','DarkRed');
// Add map1 entries to map2
map2.putAll(map1);
System.debug(map2.values());//(LightRed, 'DarkRed')

remove(key):

Map<String, String>colorCodes =   new Map<String, String>();
colorCodes.put('Red', 'FF0000');
colorCodes.put('Blue', '0000A0');
colorCodes.put('Green', '0000A0');
System.debug('printing=== '+colorCodes);// Blue=0000A0, Green=0000A0, Red=FF0000
for(String key:colorCodes.keySet().clone()) {
colorCodes.remove('Green');
system.debug(colorCodes);// Blue=0000A0, Red=FF0000
}

Values ():

Map<String, String>colorCodes = new Map<String, String>();
colorCodes.put('FF0000', 'Red');
colorCodes.put('0000A0', 'Blue');
List<String> colors = new List<String>();
colors = colorCodes.values();
system.debug(colors);//(Red, Blue)

getSObjectType()

Map <id,Account>acctMap = new map<id,account>([select  name from  Account limit 10]);
for(string accValue:acctmap.keyset()){
system.debug(acctmap.get(accValue));
}

Example How to display record on basis of alphabet

Apex class
public class DynamicSearchExample {
public Map<string,list<account>>accountsMap {get; set;}
public List<selectoption> keys {get; set;}
public String selectedKey {get; set;}
public Map<string, account>accsByName {get; set;}
public Set<string>getMapKeys(){
returnaccountsMap.keySet();
    }
publicDynamicSearchExample(){
accsByName=new Map<string, account>();
        List<string>sortedKeys=new List<string>();
accountsMap=new Map<string, list<account>>();
accountsMap.put('All', new List<account>());
        List<account>accs=[select Name, industry,type,phone from Account order by Name asc];               
for (Account acc : accs){
accountsMap.get('All').add(acc);
            String start=acc.Name.substring(0,1);
            List<account>accsFromMap=accountsMap.get(start);
if (null==accsFromMap){
accsFromMap=new List<account>();
accountsMap.put(start,accsFromMap);
            }
accsFromMap.add(acc);
accsByName.put(acc.name,acc);
        }
keys=new List<selectoption>();
for (String key : accountsMap.keySet()){
if(key != 'All'){
sortedKeys.add(key);
            }
        }
sortedKeys.sort();
sortedKeys.add('All');
for (String key : sortedKeys){
keys.add(new SelectOption(key, key));
        }
selectedKey='All';
    }
}
Visualforce page
<apex:page controller="DynamicSearchExample">
<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" data-wp-preserve="%3Cscript%3E%0Afunctionredraw_accounts()%7B%0A%0A%20%20%20%20%7D%0A%3C%2Fscript%3E" data-mce-resize="false" data-mce-placeholder="1" class="mce-object" width="20" height="20" alt="&lt;script&gt;" title="&lt;script&gt;" />
<apex:form>
<apex:actionFunction name="redraw_accounts" rerender="accs" status="status"/>
<apex:pageBlock title="Criteria">
<apex:outputLabel value="Starting Letter"/>
<apex:selectList value="{!selectedKey}" size="1" onchange="redraw_accounts()">
<apex:selectOptions value="{!keys}" />
</apex:selectList>
</apex:pageBlock>
<apex:pageBlock title="Accounts">
<apex:actionstatus id="status" startText="Loading Data..........." stopText="Loading completed....." >
<apex:facet name="start"/>
<apex:facet name="stop">
<apex:outputPanel id="accs">
<apex:pageBlockTable value="{!accountsMap[selectedKey]}" var="acc">
<apex:column value="{!acc.name}"/>
<apex:column value="{!acc.industry}"/>
<apex:column value="{!acc.type}"/>
<apex:column value="{!acc.phone}"/>
</apex:pageBlockTable>
</apex:outputPanel>
</apex:facet>
</apex:actionstatus>
</apex:pageBlock>
</apex:form>
</apex:page>

Output

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