I created a Vf page where it shows Account related object record namea with checkboxes to select and contact as picklist.
I want tosend email the selected records list to selected contact. How to add the selected contact id and selected list of records in EMail method. My code is below
 

public with sharing class Nex_Send_Email{
 private ApexPages.StandardController standardController;
 
    Private Id accID;
    public List<SysWrapper> listSysWrapper {get; set;}
    public List<NEX_System__c> selectedSystems{get;set;}
     //private final List<Id> contactids ;

  public ID contactID {get; set;}
   public List<SelectOption> contactList{get;set;}
    public string selectedContact { get; set; }
      public string selectedReseller {get;set;}
    
    
    public Nex_Send_Email(ApexPages.StandardController standardController)
    {
     accID=  ApexPages.currentPage().getParameters().get('acId');
       system.debug('accID::' +accID);
            listSysWrapper = new List<SysWrapper>();
            searchRecord();
            
       List<Contact> oContact = [select id, Name, email from Contact where AccountId=:accID and Contact_Status__c = 'Active' and email !=null];

        contactList = new List<SelectOption>();
        contactList.add(new SelectOption('','--None--'));
        for(Contact ct: oContact)
        {
            contactList.add(new SelectOption(ct.id,ct.Name+' - '+ct.email));
            contactID = ct.Id;
            system.debug('contactID ::' +contactID );       
            
            
    }
    }
    
    public void searchRecord()
    {
        listSysWrapper .clear();
            for(NEX_System__c a: [select Id, Name from NEX_System__c where Nex_Account__c=:accID AND NEX_System_State__c='Active' limit 10]) 
            {
                listSysWrapper .add(new SysWrapper(a));
            }
            system.debug('listSysWrapper ::' +listSysWrapper); 
    }

    public void processSelected() 
    {
        selectedSystems= new List<NEX_System__c>();
        selectedSystems.clear();
        for(SysWrapper wrapAccountObj : listSysWrapper) 
        {
            if(wrapAccountObj.selected == true) 
            {
                selectedSystems.add(wrapAccountObj.acc);
                 system.debug('selectedSystems::' +selectedSystems); 
            }
        }
    }

  
    


    // This is our wrapper/container class. 
    public class SysWrapper
    {
        public NEX_System__c acc {get; set;}
        public Boolean selected {get; set;}
        public SysWrapper(NEX_System__c  a) 
        {
            acc = a;
            selected = false;
        }
    }
    
     public void contactsrefresh()
    {
        system.debug('selected reseller:' +selectedReseller);
        if (selectedReseller!=null)
        {
            contactList.clear();
            List<Contact> resellercontacts = [select id, Name, email from Contact where (AccountId = :accID or AccountId = :selectedReseller) and Contact_Status__c = 'Active' and email !=null];
            contactList.add(new SelectOption('','--None--'));
            for (Contact rc :resellercontacts)
            {
                if(rc.accountid == accID)
                {
                    contactList.add(new SelectOption(rc.id,rc.Name+' - '+rc.email));
                }
            }
            for (Contact rc :resellercontacts)
            {
                if(rc.accountid != accID)
                {
                    contactList.add(new SelectOption(rc.id,rc.Name+' - '+rc.email));
                }
            }
        }
        }  
           

}

Please help to add email method and add contact as to addressa nd add list of records as subject