Contact Class Requirements

• The contact object shall have a required unique contact ID string that cannot be longer than 10 characters. The contact ID shall not be null and shall not be updatable.
• The contact object shall have a required firstName String field that cannot be longer than 10 characters. The firstName field shall not be null.
• The contact object shall have a required lastName String field that cannot be longer than 10 characters. The lastName field shall not be null.
• The contact object shall have a required phone String field that must be exactly 10 digits. The phone field shall not be null.
• The contact object shall have a required address field that must be no longer than 30 characters. The address field shall not be null.

Contact Service Requirements

• The contact service shall be able to add contacts with a unique ID.
• The contact service shall be able to delete contacts per contact ID.
• The contact service shall be able to update contact fields per contact ID. The following fields are updatable:
  • firstName
  • lastName
  • Number
  • Address

ONLY NEED HELP ON CONTACTSERVICE CLASS and I NEED A JUNIT TEST CASE. Can you make it as simple as possible ?

Java Language