Question

Suppose the abstract class Message is defined below

public abstract class Message
{
private String value;
public Message(String initial)
{
value = initial;
}

public String getMessage()
{
return value;
}

public abstract String translate();
}
A concrete subclass of Message, called FrenchMessage, is defined. Which methods must FrenchMessage define?

A. translate() only
B. getMessage() only
C. The FrenchMessage constructor and translate() only
D. The FrenchMessage constructor, getMessage(), and translate()

Answer 1

The concrete subclass FrenchMessage must define the abstract method translate() only, as it inherits the Message class constructor and getMessage() method.

Step-by-step explanation:

A student asked which methods a concrete subclass called FrenchMessage, derived from an abstract class Message, must define. Since Message is an abstract class with a defined constructor Message(String initial) and a concrete method getMessage(), the subclass FrenchMessage would inherit these without needing to redefine them unless it wants to change their behavior.

However, the abstract method translate() has no implementation in the abstract class, thus FrenchMessage must provide a concrete implementation for this method. Therefore, the correct answer is A. translate() only. Although FrenchMessage could define its own constructor, it is not mandatory unless the subclass needs to perform additional initialization tasks beyond those provided by the superclass's constructor.