Fix LoD and Add logging

src/main/java/seedu/address/logic/parser/customer/CustomerAddCommandParser.java

@@ -40,7 +40,7 @@ public CustomerAddCommand parse(String args) throws ParseException {
                 ArgumentTokenizer.tokenize(args, PREFIX_NAME, PREFIX_PHONE, PREFIX_EMAIL, PREFIX_ADDRESS);
 
         if (!arePrefixesPresent(argMultimap, PREFIX_NAME, PREFIX_ADDRESS, PREFIX_PHONE, PREFIX_EMAIL)
-                || !argMultimap.getPreamble().isEmpty()) {
+                || !argMultimap.isEmptyPreamble()) {
             logger.severe("Could not parse command");
             throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, CustomerAddCommand.MESSAGE_USAGE));
         }

src/main/java/seedu/address/logic/parser/customer/CustomerFindCommandParser.java

@@ -3,6 +3,7 @@
 import static seedu.address.logic.Messages.MESSAGE_INVALID_COMMAND_FORMAT;
 
 import java.util.Arrays;
+import java.util.logging.Logger;
 
 import seedu.address.logic.commands.customer.CustomerFindCommand;
 import seedu.address.logic.parser.Parser;
@@ -14,6 +15,8 @@
  */
 public class CustomerFindCommandParser implements Parser<CustomerFindCommand> {
 
+    private static final Logger logger = Logger.getLogger(CustomerFindCommandParser.class.getName());
+
     /**
      * Parses the given {@code String} of arguments in the context of the FindCommand
      * and returns a FindCommand object for execution.
@@ -23,6 +26,7 @@ public class CustomerFindCommandParser implements Parser<CustomerFindCommand> {
     public CustomerFindCommand parse(String args) throws ParseException {
         String trimmedArgs = args.trim();
         if (trimmedArgs.isEmpty()) {
+            logger.severe("Could not parse command");
             throw new ParseException(
                     String.format(MESSAGE_INVALID_COMMAND_FORMAT, CustomerFindCommand.MESSAGE_USAGE));
         }

src/main/java/seedu/address/logic/parser/user/UserLoginCommandParser.java

@@ -36,7 +36,7 @@ public UserLoginCommand parse(String args) throws ParseException {
                 ArgumentTokenizer.tokenize(args, PREFIX_USER, PREFIX_PASSWORD);
 
         if (!arePrefixesPresent(argMultimap, PREFIX_USER, PREFIX_PASSWORD)
-                || !argMultimap.getPreamble().isEmpty()) {
+                || !argMultimap.isEmptyPreamble()) {
             logger.severe("Could not parse command");
             throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, UserLoginCommand.MESSAGE_USAGE));
         }

src/main/java/seedu/address/logic/parser/user/UserUpdateCommandParser.java

@@ -41,7 +41,7 @@ public UserUpdateCommand parse(String args) throws ParseException {
 
         UserUpdateDescriptor userUpdateDescriptor = new UserUpdateDescriptor();
 
-        if (!argMultimap.getPreamble().isEmpty()) {
+        if (!argMultimap.isEmptyPreamble()) {
             logger.severe("Could not parse command");
             throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, UserUpdateCommand.MESSAGE_USAGE));
         }