Questions and Answers
What does the keyword 'extends' indicate?
What is the Object class in Java?
What is class hierarchy?
A set of classes related by inheritance.
What does 'protected' mean in terms of access modifiers?
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What is inheritance in object-oriented programming?
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What does the 'super' keyword do?
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Define direct superclass.
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What is meant by 'brittle software'?
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What does it mean to override a method?
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What is a clone method?
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Define indirect superclass.
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A subclass can explicitly invoke a constructor of its superclass by using the superclass constructor call syntax-keyword ______ followed by a set of parentheses containing the superclass constructor's arguments.
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Every object of a _____ is also an object of that class's _____. However, a _____ object is not an object of any of its _____.
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In a(n) _____ relationship, an object has a reference to an object of another class as a member.
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In a(n) _____ relationship, an object of a subclass type may also be treated as an object of the superclass type.
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What are standardized reusable components?
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What does private mean in terms of member access?
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What is the direct superclass of a subclass?
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With _____ inheritance, a class is derived from one superclass. Java does not support _____ inheritance.
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A subclass inherits the members of its superclass that are declared with the access specifiers _____ and _____
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Which class normally overrides the toString method?
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How does inheritance promote software reusability?
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Explain protected member access.
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Explain the difference between composition and inheritance.
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Explain the initialization process for an object of class BasePlusCommissionEmployee.
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How to invoke a superclass method from a subclass method?
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Study Notes
Java Inheritance Concepts
- Inheritance allows a subclass to inherit properties and methods from a superclass, creating a hierarchical relationship.
- The Object class serves as the ultimate superclass for all Java classes.
- Class relationships established through inheritance are termed class hierarchy.
Access Modifiers
- Protected members can be accessed within the defining class and all its subclasses, as well as other classes in the same package.
- Private members remain inaccessible to subclasses, ensuring encapsulation.
- Members declared with public and protected access specifiers are inherited by subclasses.
Keywords in Inheritance
- The extends keyword indicates that a subclass inherits from a particular superclass.
- The super keyword is used to refer to superclass members and to call a superclass constructor.
- When a subclass invokes a constructor of its superclass, it does so with the super keyword followed by the appropriate parameters.
Types of Relationships
- Is-a relationship indicates that a subclass is a specialized type of a superclass.
- Has-a relationship signifies that an object includes a reference to another object as a member.
- Inheritance leads to brittle software, where minor changes in superclasses can disrupt subclass functionality.
Method Overriding and Cloning
- Method override occurs when a subclass defines a method with the same signature as a method in its superclass.
- The clone method is a protected method that creates a copy of the object it is called on.
Composition vs. Inheritance
- Inheritance grants a new class attributes and behaviors from an existing one, allowing for dual treatment as its type and superclass types.
- Composition involves creating a new class from existing classes’ instances, where the new class typically cannot be treated as an instance of the component classes.
Object Initialization
- When creating an object of a derived class, constructors from the superclass are invoked in sequence, starting from the highest ancestor.
- In the BasePlusCommissionEmployee example, constructors are called in a chain from Object to CommissionEmployee, finally reaching BasePlusCommissionEmployee, which initializes additional attributes.
Accessing Superclass Methods
- To invoke a superclass method from an overriding subclass method, use the super keyword.
- If the subclass method does not override the superclass one, simply call the superclass method by its name with the necessary arguments.
Software Design Principles
- Standardized reusable components are a future trend in software construction, paralleling manufacturing practices in industries like automotive.
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Description
Test your understanding of key concepts from Chapter 9 of Scientific Programming. This quiz covers essential terminology relating to class inheritance, object classes, and access modifiers in Java. Flashcards are a great way to reinforce your learning and prepare for exams.