Fix more checkstyle errors

src/main/java/seedu/address/logic/parser/ListCommandParser.java

@@ -1,11 +1,11 @@
 package seedu.address.logic.parser;
 
-import java.util.List;
-
 import static seedu.address.logic.Messages.MESSAGE_INVALID_COMMAND_FORMAT;
 import static seedu.address.logic.parser.CliSyntax.PREFIX_TAG;
 import static seedu.address.logic.parser.CliSyntax.PREFIX_WARD;
 
+import java.util.List;
+
 import seedu.address.logic.commands.ListCommand;
 import seedu.address.logic.parser.exceptions.ParseException;
 import seedu.address.model.person.ListKeywordsPredicate;
@@ -23,7 +23,7 @@ public class ListCommandParser implements Parser<ListCommand> {
     public ListCommand parse(String args) throws ParseException {
         String trimmedArgs = args.trim();
         if (trimmedArgs.isEmpty()) {
-            return new ListCommand();   // return a ListCommand object with no predicate
+            return new ListCommand(); // return a ListCommand object with no predicate
         }
 
         ArgumentMultimap argMultimap =

src/main/java/seedu/address/logic/parser/ParserUtil.java

@@ -2,7 +2,11 @@
 
 import static java.util.Objects.requireNonNull;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
 
 import seedu.address.commons.core.index.Index;
 import seedu.address.commons.util.StringUtil;

src/main/java/seedu/address/model/person/ListKeywordsPredicate.java

@@ -1,7 +1,7 @@
 package seedu.address.model.person;
 
-import java.util.function.Predicate;
 import java.util.List;
+import java.util.function.Predicate;
 
 import seedu.address.commons.util.StringUtil;
 import seedu.address.commons.util.ToStringBuilder;
@@ -13,6 +13,11 @@ public class ListKeywordsPredicate implements Predicate<Person> {
     private final List<String> tagKeywords;
     private final String wardKeyword;
 
+    /**
+     * Constructs a ListKeywordsPredicate object.
+     * @param tagKeywords List of tag keywords to filter the list of persons.
+     * @param wardKeyword Ward keyword to filter the list of persons.
+     */
     public ListKeywordsPredicate(List<String> tagKeywords, String wardKeyword) {
         this.tagKeywords = tagKeywords;
         this.wardKeyword = wardKeyword;
@@ -62,6 +67,10 @@ public String toString() {
                 .toString();
     }
 
+    /**
+     * Returns a string representation of the keywords.
+     * @return String representation of the keywords.
+     */
     public String getKeywordsString() {
         String tags = "\ntags: " + tagKeywords.toString()
                 .replace("[", "")