Object-Oriented Programming: Inheritance Concepts
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Questions and Answers

Which of the following is a benefit of inheritance?

  • Software reuse (correct)
  • Higher error rates
  • Increased complexity of code
  • More usage of global variables

    • A class is an instance of an object.

    False

    What keyword is used in Java to establish an inheritance relationship?

    extends

    The visibility modifier that is accessible only by the class it belongs to is called ______.

    <p>private</p> Signup and view all the answers

    Which of these terms refers to a new class derived from an existing one?

    <p>Child class</p> Signup and view all the answers

    Overloading allows a child class to change the definition of an inherited method.

    <p>False</p> Signup and view all the answers

    What does the 'super' keyword do in Java?

    <p>It refers to the parent class and can invoke the parent's constructor.</p> Signup and view all the answers

    Match the following concepts with their definitions:

    <p>Inheritance = The process of deriving a new class from an existing class Visibility Modifiers = Control access to variables and methods in a class Overriding = Changing the definition of an inherited method in a child class Encapsulation = Restricting access to the inner workings of an object</p> Signup and view all the answers

    What does the final modifier do in a method?

    <p>The method cannot be overridden</p> Signup and view all the answers

    Inheritance is transitive, meaning inherited traits are continuously passed down.

    <p>True</p> Signup and view all the answers

    What is an abstract method?

    <p>A method header without a method body.</p> Signup and view all the answers

    A class that cannot be instantiated and serves as a placeholder is called an _____ class.

    <p>abstract</p> Signup and view all the answers

    Match the following concepts with their definitions:

    <p>Polymorphism = To have many forms Overloading = Multiple methods with the same name but different signatures Interface = A collection of abstract methods and constants Abstract class = A placeholder in a class hierarchy</p> Signup and view all the answers

    What is the purpose of overriding the toString() method?

    <p>To provide a custom string representation of the object</p> Signup and view all the answers

    Siblings in object-oriented programming hold the relationship of inheritance between each other.

    <p>False</p> Signup and view all the answers

    What are the two types of polymorphism?

    <p>Compile time and runtime.</p> Signup and view all the answers

    What is dynamic binding also known as?

    <p>Late binding</p> Signup and view all the answers

    A search pool is primarily used for sorting items.

    <p>False</p> Signup and view all the answers

    What does the compareTo method do?

    <p>It compares two inputs against each other.</p> Signup and view all the answers

    Polymorphism allows an interface reference variable to refer to an object of any class that implements the ______.

    <p>interface</p> Signup and view all the answers

    Match the following definitions with their correct terms:

    <p>Dynamic Binding = Decision made at runtime Comparable Interface = Used for comparing objects Selection Sort = Strategy involves finding the smallest element Insertion Sort = Involves inserting an item in a sorted sublist</p> Signup and view all the answers

    What does casting do in the context of method invocation?

    <p>Converts an object to an appropriate reference</p> Signup and view all the answers

    Sorting is the process of organizing a list of items in random order.

    <p>False</p> Signup and view all the answers

    Describe the strategy used in selection sort.

    <p>Find the smallest element and swap it with the first unsorted element.</p> Signup and view all the answers

    What is the purpose of binary search?

    <p>To find a target in a sorted array more efficiently than linear search.</p> Signup and view all the answers

    An array must be sorted for binary search to work.

    <p>True</p> Signup and view all the answers

    What happens if a program does not handle an exception?

    <p>The program will terminate and produce a message about the exception.</p> Signup and view all the answers

    A ___ is an object that defines an unusual or erroneous situation.

    <p>exception</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Exception = An indication of a problem in a program Error = Unrecoverable situation usually not caught Call stack trace = Shows the sequence of method calls leading to an exception Try-catch statement = Mechanism for handling exceptions in code</p> Signup and view all the answers

    Which of the following scenarios may cause an exception to be thrown?

    <p>All of the above</p> Signup and view all the answers

    An error in Java is recoverable and can be caught.

    <p>False</p> Signup and view all the answers

    What does the first line of a call stack trace indicate?

    <p>The method, file, and line number where the exception occurred.</p> Signup and view all the answers

    What is the primary purpose of the try block?

    <p>To define a block of code to be tested for errors</p> Signup and view all the answers

    The catch block is used to define a block of code that executes only if an error occurs in the try block.

    <p>True</p> Signup and view all the answers

    What happens if no exception is thrown in a try-catch statement?

    <p>Execution continues with the statements after the try block.</p> Signup and view all the answers

    The ______ is executed no matter how the try block is exited.

    <p>finally clause</p> Signup and view all the answers

    Match each term with its correct description:

    <p>Checked exceptions = Must be caught or listed in throws clause Unchecked exceptions = Do not need to be explicitly handled Throwable = Parent of both Exception and Error classes Exception variable = Used alongside getMessage method</p> Signup and view all the answers

    What does the getMessage method do?

    <p>Returns a string explaining the reason the exception was thrown</p> Signup and view all the answers

    The reserved word throw is used to start exception propagation.

    <p>True</p> Signup and view all the answers

    What is exception propagation?

    <p>It is the process where an unhandled exception is passed up to the method that invoked it until it is caught or terminates the program.</p> Signup and view all the answers

    Study Notes

    What is a class?

    • A blueprint for an object.
    • Represents the concept of an object.

    Inheritance

    • A fundamental object-oriented design technique used to create and organize reusable classes.
    • Creating new classes from scratch is expensive, inheritance makes it cheaper.
    • Process of deriving a new class (child/subclass) from an existing one (parent/superclass/base class).
    • Child class automatically "inherits" variables and methods of the original class.

    Depicting Inheritance Relationships

    • Use a solid arrow pointing to the parent class.

    Inheritance Relationships

    • Create an "is-a" relationship.

    Benefits of Inheritance

    • Software reuse: capitalize on already existing software components and saves space.

    Visibility Modifiers

    • Public: Visible everywhere.
    • Protected: Accessible within its own package and by subclasses in other packages. Provides more encapsulation than public, but less than private.
    • Private: Member can be accessed only by its own class.

    The "super" keyword

    • Refer to the parent class.
    • Often used to invoke the parent's constructor.

    Method Overriding

    • A child class can override the definition of an inherited method in favor of its own.

    Method Overloading

    • Involves multiple methods with the same name, but different signatures, within the same class.

    The "final" Modifier

    • Prevents a method from being overridden.

    Sibling Classes

    • Two classes derived from the same parent.
    • Have the same characteristics inherited from their parents, but do not have an inheritance relationship between themselves.

    Class Hierarchy

    • Common features should be established as high up in the hierarchy as possible.

    Inheritance is Transitive

    • Inherited traits are continuously passed down through the hierarchy.

    The toString() Method

    • Typically overridden to provide a custom string representation of an object.

    The equals() Method

    • Provided by the Object class, determines if two object references refer to the same object.

    Java Interfaces

    • Collection of abstract methods and constants.
    • Establish a set of methods that a class will implement.

    Abstract Methods

    • Method headers without a method body.
    • Declares a contract for a method that will be implemented by concrete subclasses.

    Implementing Interfaces

    • Use the reserved words interface and implements in the class header to use interfaces.

    Abstract Classes

    • Placeholders in a class hierarchy that represent generic concepts.
    • Cannot be instantiated.
    • Define common behavior for subclasses.

    Polymorphism

    • "Many forms."
    • Allows a message to be displayed in more than one form.
    • Defines one interface with multiple implementations.

    Polymorphic References

    • A reference can refer to different types of objects at different times.
    • The method called through a polymorphic reference can vary from one invocation to the next.

    Types of Polymorphism

    • Compile-time (Static): Determined at compile time.
    • Runtime (Dynamic): Determined at runtime.

    Binding

    • The process of associating a method call with its specific implementation.

    Dynamic Binding / Late Binding

    • The decision about which implementation to call cannot be made until runtime.

    Polymorphism via Interfaces

    • Polymorphism works similarly, but an interface reference variable can refer to objects of any class implementing that interface.

    Casting

    • Cast the appropriate reference.
    • Valid if we know the invocation is valid in a particular situation.

    Sorting

    • The process of arranging a list of items in a particular order.

    Selection Sort Strategy

    • Find the smallest element in the unsorted part of the array.
    • Swap it with the element at the beginning of the unsorted portion.
    • Repeat until the entire array is sorted.

    Swapping in Selection Sort

    • Swap two elements using a temporary variable.

    The Comparable Interface

    • Built-in Java interface from java.lang package.
    • Allows objects of a class to be compared to each other, mainly for sorting purposes.

    The compareTo() Method

    • Used to compare two objects of the same class with respect to each other.
    • Returns:
      • Negative value if the first input is less than the second.
      • 0 if they are equal.
      • Positive value if the first input is greater than the second.

    Insertion Sort Strategy

    • Pick an item and insert it into its correct place within a sorted sublist.
    • Repeat until all items have been inserted.

    Search Pool

    • A group of items.

    Searching

    • The process of finding a target element within a search pool.
    • Examine items sequentially, starting from the beginning, until the target is found or the end of the pool is reached.
    • Requires a sorted array.
    • Start at the middle index of the array.
    • If the target is not at the middle index, eliminate half of the array based on the relative order.

    Exceptions

    • Represent problems or unusual situations in a program.

    Error

    • Represents an unrecoverable situation, typically not caught.

    Exception Scenarios

    • Invalid input.
    • File not found.
    • Array out of bounds.
    • Network connectivity issues.
    • Division by zero.

    Exception Handling

    • If an exception isn't handled, the program terminates and displays an error message with the call stack trace.

    Call Stack Trace

    • Indicates the line where the exception occurred.
    • Shows the method call trail leading to the offending line.

    Try-Catch Statement

    • Identifies a block of code that may throw an exception.
    • Contains a try block and catch blocks.

    Try Block

    • Defines a block of code to be tested for errors during execution.

    Catch Block

    • Defines a block of code to be executed if an error occurs within the try block.

    Catch Clauses and Exception Variables

    • Each catch clause is a catch handler.
    • Exception variable can help in analyzing the exception.

    The getMessage() Method

    • Returns a string explaining the reason for the exception.

    Finally Clause

    • Executed regardless of how the try block is exited (exception or not).

    Exception Propagation

    • If an exception is not caught where it occurs, control goes back to the method that invoked it.
    • Continues until caught, handled, or passed out of the main method, which terminates the program.

    Defining Custom Exceptions

    • Extend the Exception class.

    The Throwable Class

    • Parent of both Exception and Error classes.
    • Superclass of all errors and exceptions.
    • Provides the basis for all descendant classes with the throw keyword.

    The throw Keyword

    • Used to explicitly throw an exception.

    Checked Exceptions

    • Must be either caught or listed in the throws clause of any method that may throw or propagate it.

    Unchecked Exceptions

    • Do not need to be explicitly declared or caught.

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    Description

    This quiz focuses on the fundamentals of inheritance in object-oriented programming. It covers key concepts such as class definitions, inheritance relationships, and visibility modifiers. Test your knowledge about how to create and use subclasses effectively.

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