Merge pull request #50 from RuijianLu/branch-AddComments

Add comment class for enabling adding comments to customers later

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

@@ -0,0 +1,60 @@
+package seedu.address.model.person;
+
+import static java.util.Objects.requireNonNull;
+import static seedu.address.commons.util.AppUtil.checkArgument;
+
+/**
+ * Represents a Person's comment the user made in the address book.
+ */
+public class Comment {
+
+    public static final String MESSAGE_CONSTRAINTS =
+            "comments should only contain alphanumeric characters and spaces, and it should not be blank";
+
+    public static final String VALIDATION_REGEX = "[\\p{Alnum}][\\p{Alnum} ]*";
+    public final String fullComment;
+
+    /**
+     * Constructs a {@code Comment}.
+     *
+     * @param comment A valid comment.
+     */
+    public Comment(String comment) {
+        requireNonNull(comment);
+        checkArgument(isValidComment(comment), MESSAGE_CONSTRAINTS);
+        fullComment = comment;
+    }
+
+    /**
+     * Returns true if a given string is a valid comment.
+     */
+    public static boolean isValidComment(String test) {
+        return test.matches(VALIDATION_REGEX);
+    }
+
+    @Override
+    public String toString() {
+        return fullComment;
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) {
+            return true;
+        }
+
+        // instanceof handles nulls
+        if (!(other instanceof Name)) {
+            return false;
+        }
+
+        Name otherName = (Name) other;
+        return fullComment.equals(otherName.fullName);
+    }
+
+    @Override
+    public int hashCode() {
+        return fullComment.hashCode();
+    }
+
+}