Questions and Answers
Interfaces in Java can only contain method declarations, not method implementations.
True
Delegation in object-oriented programming refers to a class inheriting the characteristics of another class.
False
Run-time polymorphism allows methods to be determined at compile time.
False
Encapsulation restricts direct access to some of an object's components in order to protect the integrity of the object.
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Inclusion polymorphism allows a variable to reference objects of different classes within the same class hierarchy.
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Each class in Java is allowed to implement multiple interfaces.
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Parameters for method definitions can only be of primitive data types in Java.
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Polymorphism enables the same method to perform different tasks based on the object that invokes it.
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In Java, an interface cannot contain any methods with implementations.
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Delegation is considered more appropriate than inheritance in many scenarios.
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Overloading methods requires that the methods differ in their return type.
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Encapsulation is the concept of restricting access to certain details of an object.
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In polymorphism, a method can be executed in different ways depending on the object type it is called on.
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Inheritance allows one class to inherit attributes and methods from multiple classes.
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Parametric polymorphism refers to the use of generics in Java.
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A class can have multiple constructors with the same name as long as they have different return types.
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Java VM errors and hardware problems are typically exceptions that are caught and handled.
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RuntimeExceptions in Java typically indicate programming errors, commonly known as bugs.
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The 'finally' block in Java is executed only if an exception occurs during the execution of the try block.
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It is mandatory for every try block in Java to have at least one catch or finally block.
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Checked exceptions in Java are exceptions that can be anticipated and must be declared in the method signature.
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In Java, the catch blocks can handle only one type of exception each.
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Delegation in Java refers to an object handling requests by passing them to a helper object.
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Polymorphism in Java allows methods to perform different functions depending on the object calling them.
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Study Notes
Exception Handling
-
Try-with-resources statement: Automatically closes resources implementing
java.io.AutoCloseable
after execution. -
Error Types:
- Errors (e.g.,
InternalError
,OutOfMemoryError
) related to JVM or hardware, typically not caught or thrown. - Runtime Exceptions (e.g.,
ArrayIndexOutOfBoundsException
), indicate programming bugs that may lead to application failures. - Exceptions (checked exceptions), expected issues that need handling (e.g.,
IOException
).
- Errors (e.g.,
-
Exception Handling Structure:
- try block: Contains code where exceptions may occur.
- catch block: Handles specific exceptions with associated code to resolve issues.
- finally block: Executes code irrespective of exceptions, cleanup operations often placed here.
Object-Oriented Concepts in Java
-
Key Concepts:
- Object: An instance of a class.
- Encapsulation: Restricting access to certain components, enhancing security.
- Class: Blueprint for creating objects.
- Interface: Defines a contract that implementing classes must adhere to.
- Inheritance: Mechanism where one class inherits properties from another.
- Delegation: Assigning responsibility for an operation to another object.
- Polymorphism: Ability to present the same interface for different underlying forms.
Polymorphism
- Inclusion Polymorphism: A single variable can refer to objects of different classes within the same hierarchy or that implement the same interface.
- Operation Polymorphism: Method overloading with the same name but different parameter lists; cannot differ by return type alone.
- Parametric Polymorphism: Use of generics to define classes and methods with type parameters to increase code reusability and flexibility.
Delegation
- Delegation Concept: A class can delegate operations to another class, often favouring delegation over inheritance for cleaner designs.
- Event-Driven Models: Often leverage delegation for event handling within applications, enhancing modularity.
Exception Throwing
- Exceptions are thrown within methods. These can be caught and handled using the previously mentioned
try-catch-finally
structure. Eachtry
block must include at least onecatch
orfinally
block unless used in atry-with-resources
.
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Description
This quiz focuses on Object-Oriented Programming concepts in Java, specifically on the try-with-resources statement and implementations of the AutoCloseable interface. Test your understanding of key OO principles including encapsulation, inheritance, and more. Perfect for students preparing for the 2024 curriculum.