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Questions and Answers
Does a subclass need to have a constructor?
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?
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?
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?
If a class does not extend any class, what happens?
A subclass can be extended by another class to become a superclass.
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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