refactor: make functions static

src/EMail.java

@@ -6,7 +6,7 @@ public class EMail {
 	 * @param email The email address being checked
 	 * @return <code>true</code> if the email is correctly formatted, otherwise <code>false</code>
 	 */
-	public boolean validate(String email) {
+	public static boolean validate(String email) {
 		// Set up regex for email format
 		String emailRegex = "[^@ \\t\\r\\n]+@[^@ \\t\\r\\n]+\\.[^@ \\t\\r\\n]+";
 		Pattern pattern = Pattern.compile(emailRegex);
@@ -20,7 +20,7 @@ public class EMail {
 	 * @param email A valid email address
 	 * @return The domain of the email address from the parameter
 	 */
-	public String getDomain(String email) {
+	public static String getDomain(String email) {
 		// Checks that the email address is valid, otherwise throw exception
 		if (!validate(email)) {
 			throw new IllegalArgumentException("The email address provided is not valid");

src/ReadFile.java

@@ -10,7 +10,7 @@ public class ReadFile {
 	 * @param filename the name of the file with, only allowing a .txt extension
 	 * @return The contents of the file
 	 */
-	public List<String> open(String filename) {
+	public static List<String> open(String filename) {
 		// Check that the filetype is correct, otherwise, throw IllegalArgumentException
 		if (!filename.endsWith(".txt")) {
 			throw new IllegalArgumentException("The filename is not a .txt format");