Object-Oriented Programming Quiz
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Questions and Answers

The _________ construct defines a new type that can group data and methods to form an object.

class

A class' ____________ indicate all operations a class user can perform on the object.

public member methods

What is the difference between accessors and mutators?

A mutator method modifies a class' fields, while an accessor method accesses fields without modification.

A class' private helper method can be called from main(), which is defined in another class.

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

A private helper method cannot call another private helper method.

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

A constructor that can be called without any arguments is called a _______________.

<p>default constructor</p> Signup and view all the answers

The default constructor is called when an object is created of the class type.

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

What is the purpose of method overloading?

<p>To provide different initialization values by defining multiple constructors with differing parameter types.</p> Signup and view all the answers

Define reference.

<p>A reference is a variable type that refers to an object, storing the memory address of that object.</p> Signup and view all the answers

What is the difference between primitive and reference type?

<p>Primitive type variables directly store data, while reference type variables refer to objects.</p> Signup and view all the answers

What are some of the functions wrapper classes allow?

<p>Wrapper classes store a single primitive type value and provide methods for type conversion and representation.</p> Signup and view all the answers

What does it mean when a wrapper class is immutable?

<p>It means the object cannot be changed after creation.</p> Signup and view all the answers

For reference variables of wrapper classes, you SHOULD use the equality operators == and != when comparing values.

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

What is the difference between autoboxing and unboxing?

<p>Autoboxing is the conversion of primitive types to wrapper classes; unboxing is the conversion of wrapper objects to primitive types.</p> Signup and view all the answers

The value of an Integer passed to a method can be modified within the method.

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

A parameter of reference type allows a method to access the class members of the object to which the parameter refers.

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

Study Notes

Classes and Methods

  • A class defines a new type that groups data and methods, forming an object.
  • Public member methods indicate all operations that can be performed by a class user on the object.
  • The member access operator (".") is used to invoke a method on an object.

Accessors and Mutators

  • Mutator methods modify a class's fields (including private fields).
  • Accessor methods can access but not modify a class's fields.
  • Mutators are known as setters (prefix "set") and accessors as getters (prefix "get").

Method Accessibility

  • Private methods of a class cannot be called from main() if defined in another class (False).
  • A private helper method can call another private helper method within the same class (False).

Constructors

  • A constructor that takes no arguments is known as a default constructor.
  • True: Default constructor is invoked when an object of the class type is created.
  • Method overloading allows defining multiple constructors with different parameter types for flexible initialization.

References

  • A reference is a variable type that points to an object and stores the object's memory address.
  • Reference types include variables of class data types and array types.

Primitive vs. Reference Types

  • Primitive type variables directly store data (e.g., int, double, char) and have fixed sizes.
  • Reference type variables refer to instances of classes (objects) and store references to data in heap space.

Wrapper Classes

  • Wrapper classes create objects to store single primitive type values (e.g., Integer, Double).
  • They provide methods for converting between primitive types and different number systems, including string representation.
  • Wrapper class objects are immutable, meaning their values cannot be changed after creation.

Equality and Comparisons

  • Using == and != for comparing reference variables of wrapper classes is False; instead, equals() and compareTo() should be used for comparing wrapper class objects.
  • When comparing a wrapper class object to a primitive variable, == can be used.

Autoboxing and Unboxing

  • Autoboxing is the automatic conversion of primitive types into their corresponding wrapper classes.
  • Unboxing is the automatic conversion of wrapper class objects back into their corresponding primitive types.

Method Parameters

  • False: An Integer object passed to a method cannot be modified; it is immutable.
  • Assigning a new value to an Integer parameter in a method creates a new Integer object.
  • A method parameter of reference type allows access to the class members of the referenced object; true since the reference is copied.

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Description

Test your knowledge of object-oriented programming concepts with this quiz. Covering topics like classes, member methods, and operators, this quiz will help reinforce your understanding of OOP principles.

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