Add Java documentation for some classes.

These classes are:
	Parser
	UserInputChecker
	CmdType
	Task
	ToDo
	Deadline
	Event
	WessyException
	CommandNotFoundException
	MissingSpacingException
	TimeSpecifierException
	UnspecifiedTimeException
	EmptyListException
	InvalidIntegerException
	NotAnIntegerException
	NotPositiveIntegerException
	MissingInputException
	TooManyInputException

build.gradle

@@ -11,7 +11,7 @@ repositories {
 dependencies {
     testImplementation group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.5.0'
     testRuntimeOnly group: 'org.junit.jupiter', name: 'junit-jupiter-engine', version: '5.5.0'
-    
+
 }
 
 test {

src/main/java/wessy/CmdType.java

@@ -2,8 +2,11 @@
 
 import java.util.Map;
 import java.util.HashMap;
-import java.util.Set;
 
+/**
+ * CmdType is an enumeration that represents all the different types of commands
+ * "Wessy" takes in.
+ */
 public enum CmdType {
     LIST("list"),
     BYE("bye"),
@@ -17,11 +20,6 @@ public enum CmdType {
 
     private final String cmd;
     private static final Map<String, CmdType> COMMANDS = new HashMap<>();
-
-    CmdType(String str) {
-        this.cmd = str;
-    }
-
     static {
         COMMANDS.put("bye", CmdType.BYE);
         COMMANDS.put("list", CmdType.LIST);
@@ -34,19 +32,39 @@ public enum CmdType {
         COMMANDS.put("clear", CmdType.CLEAR);
     }
 
-    public static CmdType getCmdType(String str) {
-        return COMMANDS.get(str);
+    /** Constructs an instance of CmdType that corresponds to the different
+     * types of commands, along with the command in its text form.
+     */
+    CmdType(String str) {
+        this.cmd = str;
     }
 
-    public static Set<String> getKeys() {
-        return COMMANDS.keySet();
+    /**
+     * Converts a command (if valid) from its text form to the corresponding
+     * CmdType.
+     *
+     * @param str Specified command in its text form.
+     * @return A CmdType that corresponds to str.
+     */
+    public static CmdType getCmdType(String str) {
+        return COMMANDS.get(str);
     }
 
+    /**
+     * Converts CmdType to command in its text form.
+     *
+     * @return The text form of the command when it is of CmdType type.
+     */
     @Override
     public String toString() {
         return cmd;
     }
 
+    /**
+     * Gets the length of the string when the command is in its text form.
+     *
+     * @return The length of string when the command is in its text form.
+     */
     public int len() {
         return cmd.length();
     }

src/main/java/wessy/Parser.java

@@ -4,7 +4,19 @@
 import java.time.LocalDateTime;
 import java.time.format.DateTimeParseException;
 
+/**
+ * Parser is a utility class that mainly processes the user input when "Wessy"
+ * first receives it. While it checks for some formats of the String, it
+ * delegates checking of the other formatting issues to UserInputChecker class.
+ */
 public class Parser {
+    /**
+     * Converts the first word in the line of user input, to the corresponding
+     * CmdType, if it is a valid command type.
+     *
+     * @param userInput The line which the user inputs.
+     * @return The corresponding CmdType, if the first word is a valid command.
+     */
     static CmdType getCmd(String userInput) {
         int idx = userInput.indexOf(' ');
         if (idx == -1) {
@@ -13,7 +25,18 @@ static CmdType getCmd(String userInput) {
         return CmdType.getCmdType(userInput.substring(0, idx));
     }
 
-    // Only for Deadline, Event & ToDo commands
+    /**
+     * Parses the line of user input and chunks it into the different components
+     * required to initialise a ToDo, Deadline or Event object. The components
+     * are possibly the task description, and the timings specified for the
+     * deadline task or the event.
+     *
+     * @param userInput The line which the user inputs.
+     * @param cmd The command specified, in the form of CmdType. It only accepts
+     *           CmdType.TODO, CmdType.DEADLINE and CmdType.EVENT.
+     * @return An array of Strings consisting of the components required to
+     * initialise a task.
+     */
     static String[] getTaskComponents(String userInput, CmdType cmd) {
         String byStr = "/by";
         String fromStr = "/from";
@@ -38,7 +61,17 @@ static String[] getTaskComponents(String userInput, CmdType cmd) {
         return new String[0];
     }
 
-    public static LocalDateTime parseDateTime(String str) throws DateTimeParseException {
+    /**
+     * Parses the input str and converts it into a LocalDateTime object.
+     *
+     * @param str The specified date and time as a String.
+     * @return A LocalDateTime object that is represented by str, in its String
+     * form.
+     * @throws DateTimeParseException If the format of str is wrong and thus
+     * cannot be parsed into a LocalDateTime object.
+     */
+    public static LocalDateTime parseDateTime(String str) throws
+            DateTimeParseException {
         str = removeSpacePadding(str);
         if (count(str, ':') == 2) {
             return LocalDateTime.parse(str);
@@ -62,6 +95,14 @@ public static LocalDateTime parseDateTime(String str) throws DateTimeParseExcept
         return LocalDateTime.parse(parseDate(str.substring(0, idx)) + "T" + str.substring(idx + 1, idx + 3) + ":" + str.substring(idx + 3) + ":00");
     }
 
+    /**
+     * Counts the number of occurrence "target" appears in str.
+     *
+     * @param str The String we scan through while counting the number of
+     *            occurrence.
+     * @param target The character we look out for when scanning through str.
+     * @return The number of occurrence "target" appears in str.
+     */
     static int count(String str, char target) {
         int num = 0;
         for (int i = 0; i < str.length(); i++) {
@@ -72,7 +113,15 @@ static int count(String str, char target) {
         return num;
     }
 
-    // Used in parseDateTime
+    /**
+     * Standardises format of date and time in str, by say making sure that the
+     * separator in the date is "-" instead of "/", making sure the date has 8
+     * digits. This is to prepare for the execution of parseDateTime(...).
+     *
+     * @param str The specified date and time in String form.
+     * @return A standardised String format of the specified date and time.
+     * @throws DateTimeParseException If str does not represent any date and time.
+     */
     static String parseDate(String str) throws DateTimeParseException {
         try {
             String[] components = str.split("-", 3);
@@ -93,15 +142,32 @@ static String parseDate(String str) throws DateTimeParseException {
         }
     }
 
-    public static int parseInt(String userInput, CmdType cmd) throws NotPositiveIntegerException {
-        int num = Integer.parseInt(removeSpacePadding(userInput.substring(cmd.len())));
+    /**
+     * Removes the command word from the user input and then the space paddings
+     * on the 2 sides. Afterwards, converts the processed String into a integer
+     * using Integer.parseInt(...).
+     *
+     * @param userInput The String to be parsed to an integer.
+     * @param cmd The specified command.
+     * @return The integer to which the String is converted.
+     * @throws NotPositiveIntegerException If the output integer is not positive.
+     */
+    public static int parseInt(String userInput, CmdType cmd) throws
+            NotPositiveIntegerException {
+        int num = Integer.parseInt(removeSpacePadding(userInput.substring(
+                cmd.len())));
             if (num <= 0) {
                 throw new NotPositiveIntegerException();
             }
         return num;
     }
 
-    // HELPER FUNC
+    /**
+     * A helper function that removes the space paddings on the two ends of str.
+     *
+     * @param str The String to be processed.
+     * @return The shorter String after removing the space paddings on the two ends.
+     */
     public static String removeSpacePadding(String str) {
         int start = 0;
         while (str.charAt(start) == ' ') {

src/main/java/wessy/Storage.java

@@ -1,6 +1,5 @@
 package wessy;
 
-import wessy.Parser;
 import wessy.task.Deadline;
 import wessy.task.Event;
 import wessy.task.ToDo;
@@ -15,10 +14,18 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 
+/**
+ *
+ */
 public class Storage {
     private final String folderPath;
     private final String fileName;
 
+    /**
+     * Constructs an instance of Storage.
+     *
+     * @param filePath
+     */
     public Storage(String filePath) {
         int lastIdx = filePath.lastIndexOf('/');
         if (lastIdx == -1) {
@@ -30,14 +37,29 @@ public Storage(String filePath) {
         }
     }
 
+    /**
+     * Constructs an instance of Storage.
+     */
     public Storage() {
         this("data/savedTasks.txt");
     }
 
+    /**
+     *
+     *
+     * @return
+     */
     String getFullPath() {
         return folderPath + "/" + fileName;
     }
 
+    /**
+     *
+     *
+     * @return
+     * @throws SecurityException
+     * @throws IOException
+     */
     List<Task> load() throws SecurityException, IOException {
         List<Task> tasks = new ArrayList<Task>();
         File savedFile = new File(folderPath + "/" + fileName);
@@ -62,6 +84,14 @@ List<Task> load() throws SecurityException, IOException {
         return tasks;
     }
 
+    /**
+     *
+     *
+     * @param tasksAsStr
+     * @return
+     * @throws IOException
+     * @throws SecurityException
+     */
     void save(String tasksAsStr) throws IOException, SecurityException {
         // CREATE FOLDERS
         Path path = Paths.get(folderPath);