Prevent Duplicate Records in Salesforce by Comparing more than one fields

Quick Summary on Logic:

      The below trigger written in Lead object using equals and hashCode Method. This methods are used on uniqueness.  Each hashCode value is unique. 

For example: test@mail.com and Test@mail.com will provide different hashCode values.

Object: Lead

Logic: If Lead record contains same Email and Company Name, then the below trigger will prevent duplication.

Apex Class

1. public class DeDupeWrapper
2. {
3.     public String email;
4.     public String company;
5.    
6.     public DeDupeWrapper(String email, String company)
7.     {
8.         this.email = email != null ? email.toLowerCase() : email;
9.         this.company = company != null ? company.toLowerCase() : company;
10.     }
11.    
12.     public Boolean equals(Object obj)
13.     {
14.         if (obj instanceof DeDupeWrapper)
15.         {
16.             DeDupeWrapper p = (DeDupeWrapper)obj;
17.             return ((email == p.email) && (company == p.company));
18.         }
19.         return false;
20.     }
21.    
22.     public Integer hashCode()
23.     {
24.         return (email.hashCode() * company.hashCode());
25.     }
26. }

Apex Trigger

1. trigger DeDuplicateLead on Lead(before insert, before update)
2. {
3.     Map<DeDupeWrapper, Lead> leadMap = new Map<DeDupeWrapper, Lead>();
4.     Map<String, String> duplicateMap = new Map<String, String>();
5.    
6.     for (Lead currLead: Trigger.new)
7.     {
8.       if((Trigger.isInsert && (currLead.Email != null && currLead.company != null))  ||
9.            (Trigger.isUpdate && (currLead.Email != Trigger.oldMap.get(currLead.Id).Email ||
10.                                  currLead.Company != Trigger.oldMap.get(currLead.Id).Company)))
11.         {
12.            
13.             DeDupeWrapper key = new DeDupeWrapper(currLead.Email, currLead.Company);
14.            
15.             if (leadMap.containsKey(key))
16.             {
17.                 currLead.Email.addError('DUPLICATE CAUGHT...!');
18.             }
19.             else
20.             {
21.                 leadMap.put(key, currLead);
22.             }
23.         }
24.     }
25.    
26.     for(DeDupeWrapper currWrap : leadMap.keySet())
27.     {
28.         duplicateMap.put(currWrap.Email, currWrap.company);
29.     }
30.    
31.     for (Lead lead : [SELECT Email,Company FROM Lead WHERE Email in: duplicateMap.keySet() AND Company in: duplicateMap.values()])
32.     {
33.         DeDupeWrapper key = new DeDupeWrapper(lead.Email, lead.Company);
34.         Lead newLead = leadMap.get(key);
35.         if(newLead != null)
36.         {
37.             newLead.addError('DUPLICATE RECORD ALREADY FOUND');
38.         }
39.     }
40. }

Reference: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/langCon_apex_collections_maps_keys_userdefined.htm