Before Insert or Upsert list must not have two identically equal elements even after instantiating within for loop

Question

I have created this following class and test class below. My question is in my class in Line X(commented line X) if i use that instead of Line Y I am receiving the above mentioned error. I put the debug logs and noticed that as the loop continues to add contacts to the list the Account Id for all the contacts so far in the list is being updated to the current Account Id that is being looped but if i use the Line Y this is not the case.

The Line X way is ultimately creating a new instance of Contact record with some prepopulated values right? Appreciate the clarification.

Class:

public class AddPrimaryContact implements Queueable {

Contact con = new Contact();
    String state;
    //List<Contact> conList;

    public AddPrimaryContact(Contact conArgu, String stateArgu){
        this.con = conArgu;
        this.state = stateArgu;        
    }   

    public void execute(QueueableContext context) {

        //String stateLoc = this.state;
        List<Account> accList = new List<Account>([SELECT Id FROM Account WHERE BillingState = :state LIMIT 200]);
        List<Contact> conList = new List<Contact>();
        for(Account acc : accList){            
            //Contact newCon = (Contact)con; // Line X 
            Contact newCon = con.clone(false,false,false,false); // Line Y
            newCon.AccountId = acc.Id;
            conList.add(newCon);
            system.debug(conList);
        }
        insert conList;
    }
}

Here is my test class:

@isTest


public class AddPrimaryContactTest {

    @isTest static void testAccountInsert() {

        List<Account> testAccList = new List<Account>();
        List<Account> testAccList1 = new List<Account>();
        //String AccState = 'IL'
        for(integer i =0; i< 100; i++){
            if(i < 50){
                Account acc = new Account(Name = 'Test' + i, BillingState = 'NY');
                testAccList.add(acc);
            }
            else{
                Account acc = new Account(Name = 'Test' + i, BillingState = 'CA');
                testAccList1.add(acc);
            }

        }
        insert testAccList;
        insert testAccList1;

        Contact con = new Contact(LastName = 'testCon');
        insert con;

        AddPrimaryContact apc = new AddPrimaryContact(con, 'NY');
        AddPrimaryContact apc1 = new AddPrimaryContact(con, 'CA');

        Test.startTest();
        System.enqueueJob(apc);
        System.enqueueJob(apc1);
        Test.stopTest();

        System.assertEquals(50, [SELECT count() FROM Contact WHERE AccountId IN :testAccList1]);

    }
}

Answer 1

Line X is not creating a new instance of contact. It's merely typecasting earlier initialized contact to 'Contact' again(curious about why would you do that), implying nothing has changed, no new contact instance is created. Now this same contact with same contactId is being added to contact list multiple times, although accountIds are different. This has caused the error that you got, list to be inserted has duplicate records.

Also I noted that your code does not save, it gives error. Are you sure you are not missing anything?

duplicate value found: duplicates value on record with id: