Please find my below batcjh class.In this batch i calling a future method from finish method which make a callout to external system.I read from the documentation that We can calll future method from finish method But while i call the future methid i get the error:
First error: Too many future calls: 1

global with sharing class errorinBatch implements Database.Batchable<SObject>,Database.stateful {
global set <String> log;
global database.QueryLocator start(Database.BatchableContext bc){
string query='select id,name,Description,CurrentGenerators__c from opportunity';
system.debug(database.getQueryLocator(query));
return database.getQueryLocator(query);
}
global void execute(Database.BatchableContext bc,List<SObject> scope){
System.debug(scope);
System.debug('====>>>>>'+scope.size());
//List<Opportunity> opp=new List<Opportunity>();
if(scope.size()>0){
for(Opportunity op:(List<Opportunity>)scope){
System.debug(op.Name);
op.Description=op.CurrentGenerators__c;
// opp.add(op);
}
}
database.SaveResult[] result=database.update(scope,false);
System.debug('====>Result'+result);
Integer rsize=result.size();
for(integer i=0;i<rsize;i++){
System.debug('for loop Block');
System.debug('====>Result[0]'+result[0]);
System.debug('=====>'+i);
System.debug('+++++>>'+scope[i].Id);
if(!result[i].isSuccess()){
log=new Set<String>();
log.add('Error in Opportunity'+scope[i].Id+'Error Message'+result[i].getErrors()[0].getMessage());
System.debug(log);
}
else {
system.debug('+++++>>> updated successfully');
}
}
}
global void finish (Database.BatchableContext bc){
Future_Schedule_Call_Example.show('cdeeuhwidhi');
}
}

Please help.

Thanks,
Deepak​​​​​​​