Hi all , when i am uploading csv file to create a new account, conatct and oppotunity i need to check account duplicate name. If not exist i need to create new  account else it must show the error message that account name already exist. i need to achevie this uiong apex code. Kindly anyone tell how to resolve this.

Apex code:

public class FileUploaderAll
{

public FileUploaderAll(ApexPages.StandardController controller) {

}

public PageReference fileAccess() {
return null;
}

public FileUploaderAll(){

}
public string nameFile{get;set;}
public Blob contentFile{get;set;}
String[] filelines = new String[]{};
List<Account> accstoupload;
List<Contact> contoupload;
List<Opportunity> opptoupload;
List<CustomLead__c> custtoupload;

public Pagereference ReadFile()
{
nameFile=contentFile.toString();
filelines = nameFile.split('\n');
accstoupload = new List<Account>();
contoupload = new List<Contact>();
opptoupload = new List<Opportunity>();
custtoupload = new List<CustomLead__c>();
for (Integer i=1;i<filelines.size();i++)
{
String[] inputvalues = new String[]{};
inputvalues = filelines[i].split(',');


Account a = new Account();
a.Name = inputvalues[0];

accstoupload.add(a);
}
try
{
insert accstoupload;
}
catch (Exception e)
{
ApexPages.Message errormsg = new ApexPages.Message(ApexPages.severity.ERROR,'An error has occured. Please check the template or try again later');
ApexPages.addMessage(errormsg);
}

//return null;
for (Integer i=1;i<filelines.size();i++)
{
String[] inputconvalues = new String[]{};
inputconvalues = filelines[i].split(',');

Contact con = new Contact();
for(account a: accstoupload)
{
con.AccountId = accstoupload[i-1].id;
//con.AccountId = a.Id;
}
//con.Account= inputconvalues[0];
con.Lastname = inputconvalues[1];
con.Lastname_lead__c = inputconvalues[2];

contoupload.add(con);
}

try
{
insert contoupload;
}
catch (Exception e1)
{
ApexPages.Message errormsg = new ApexPages.Message(ApexPages.severity.ERROR,'An error has occured. Please check the template or try again later');
ApexPages.addMessage(errormsg);
}
// return null;

for (Integer i=1;i<filelines.size();i++)
{
String[] inputvalues = new String[]{};
inputvalues = filelines[i].split(',');

Opportunity opp = new Opportunity();
for(account a: accstoupload)
{
opp.AccountId = accstoupload[i-1].id;
//opp.AccountId = a.Id;
}
opp.Name = inputvalues[3];
opp.OPP_DateOfBirth__c = inputvalues[4];
opp.StageName = inputvalues[6];
opp.CloseDate = date.parse(inputvalues[5]);
// a.ShippingPostalCode = inputvalues[4];
// a.ShippingCountry = inputvalues[5];

opptoupload.add(opp);
}

try
{
insert opptoupload;
}
catch (Exception e2)
{
ApexPages.Message errormsg = new ApexPages.Message(ApexPages.severity.ERROR,'An error has occured. Please check the template or try again later');
ApexPages.addMessage(errormsg);
}
for (Integer i=1;i<filelines.size();i++)
{
String[] inputcustvalues = new String[]{};
inputcustvalues = filelines[i].split(',');


CustomLead__c cust = new CustomLead__c();
cust.CompanyName__c = inputcustvalues[0];
cust.LastName_c__c = inputcustvalues[1];
cust.Name = inputcustvalues[2];
cust.opp_name__c = inputcustvalues[3];

custtoupload.add(cust);
}
try
{
insert custtoupload;
}
catch (Exception e3)
{
ApexPages.Message errormsg = new ApexPages.Message(ApexPages.severity.ERROR,'An error has occured. Please check the template or try again later');
ApexPages.addMessage(errormsg);
}
return null;
}
public List<Account> getuploadedAccounts()
{
if (accstoupload!= NULL)
if (accstoupload.size() > 0)
return accstoupload;
else
return null;
else
return null;
}

public List<Contact> getuploadedContact()
{
if (contoupload!= NULL)
if (contoupload.size() > 0)
return contoupload;
else
return null;
else
return null;
}

public List<Opportunity> getuploadedOpportunity()
{
if (opptoupload!= NULL)
if (opptoupload.size() > 0)
return opptoupload;
else
return null;
else
return null;
}
public List<CustomLead__c> getuploadedCustomLead()
{
if (custtoupload!= NULL)
if (custtoupload.size() > 0)
return custtoupload;
else
return null;
else
return null;
}
/* public pageReference fileAccess(){
Document lstDoc = [select id,name,Body from Document where name = 'test'];

System.Debug('DOC NAME :: '+lstDoc.name);
System.Debug('DOCBODY :: '+lstDoc.Body);


return null;
} */

public static testMethod void testReadFile1() {

Document lstDoc = [select id,name,Body from Document where name = 'test'];

// System.Debug('DOC NAME :: '+lstDoc.name);
//System.Debug('DOCBODY :: '+lstDoc.Body);
FileUploader file=new FileUploader();
Blob content= lstDoc.Body;
file.nameFile=content.toString();

}

public static testMethod void testReadFile2() {

}

}