Questions and Answers
Does a subclass need to have a constructor?
Yes, the subclass has its own constructor, either explicit or implicitly created.
How does a subclass call the superclass constructor?
Using the super keyword in the first line of the subclass constructor.
If a superclass constructor exists and a subclass doesn't explicitly call that constructor, what happens?
Java implicitly calls the no-argument superclass constructor.
If a class does not extend any class, what happens?
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A subclass can be extended by another class to become a superclass.
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Study Notes
Subclass Constructors
- A subclass must have its own constructor, which can be either defined explicitly or created implicitly by Java.
- To invoke a superclass constructor from a subclass, the
superkeyword must be used as the first statement in the subclass constructor.
Superclass Constructor Behavior
- If a superclass has a constructor and the subclass does not explicitly call it, Java automatically calls the no-argument constructor of the superclass.
- If a class does not extend another class, it implicitly extends the Object class, which is the root of all Java classes.
Subclass Relationships
- A subclass can itself be extended by another class, allowing it to function as a superclass for future subclasses.
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Description
Test your understanding of subclass constructors in Java. This quiz covers how to define constructors in subclasses, the invocation of superclass constructors using the 'super' keyword, and the relationships between subclasses and superclasses. Challenge your knowledge of object-oriented programming concepts!
