[SalesForce] Compile Error: Illegal assignment from Decimal to Integer

itemlst.Quantity = templook[i].Quantity__c;

Here Quantity is of integer type and Quantity_c is of decimal type.How can I convert Quantity_c into Integer

itemlst.Quantity = integer.valueOf(templook[i].Quantity__c);

Integer.valueOf will work.

Edit:

 Decimal myDecimal = 4.12;
 Integer a=myDecimal.intValue();
  System.debug('*****'+a);

I used Decimal.intValue() and it works as shown.

Try changing integer.valueof(csvRecordData[8]); to decimal.valueof(csvRecordData[8]);

The clause in your SOQL

where Month__c =: month and Year__c =: year and Reference_Number__c =: ref

and the error message

Invalid bind expression type of String for column of type Decimal at line 395 column 176

is most likely, as @Himanshu said that Reference_Number__c is a field of type Number but local variable ref is of type String. Change to:

where Month__c =: month and Year__c =: year and Reference_Number__c =: Decimal.valueOf(ref)