Java Basics: Constructors and Identifiers

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Questions and Answers

What is the primary characteristic of a default constructor?

It initializes all fields with specific values provided by the user.

It can only be used within an internal class.

It is parameterless and sets fields to default values. (correct)

It is parameterized and requires at least one argument.

Which statement correctly describes the visibility of a default constructor based on class type?

It can be set to internal visibility only in internal classes.

It will be private if the class is private and public if the class is public. (correct)

It is always public irrespective of the class type.

It can be private only if the class is declared as abstract.

What happens to numeric fields in a class when a default constructor is called?

They are converted to strings.

They retain their last known values.

They are initialized to 0. (correct)

They are set to their maximum values.

What is the significance of a method having a return type of void?

It means the method will not return any value. Signup and view all the answers

Which of the following statements about default values set by a default constructor is accurate?

Objects are set to null. Signup and view all the answers

What prevents falling through a switch case in C#?

break Signup and view all the answers

In C#, what does the default keyword do in the context of method parameters?

Assigns a value if no value is provided Signup and view all the answers

Which of the following correctly describes a 'case' in a switch statement in C#?

A value that the switch expression could match Signup and view all the answers

What component encompasses everything in the curly braces of a method in C#?

Method body Signup and view all the answers

Which statement about the keyword 'end' in C# is correct?

It does not exist in C# Signup and view all the answers

What is a constructor primarily used for in object-oriented programming?

To initialize new objects of a class Signup and view all the answers

What happens when no default value is set for a parameter in a method?

The parameter is assigned a value of null Signup and view all the answers

In the context of collections in C#, which statement is true?

Collections allow dynamic resizing Signup and view all the answers

Which of the following must be identical when overriding a method in a derived class?

Visibility Signup and view all the answers

What access level should be used for members to ensure they are accessible only to the class methods and its child classes?

protected Signup and view all the answers

What is a key distinction between abstract classes and interfaces in C#?

Abstract classes can have both abstract and non-abstract methods. Signup and view all the answers

In method overriding, which of these are NOT required to be the same as the parent class's method?

Method implementation Signup and view all the answers

When defining an abstract class in C#, what must it contain?

Both abstract and non-abstract methods Signup and view all the answers

What is NOT a requirement for a method in a derived class to correctly override a virtual method?

Same access level as the parent method Signup and view all the answers

Which statement is true regarding method overriding in C#?

The derived method can include additional parameters if they are optional. Signup and view all the answers

Which option describes an abstract method correctly?

It cannot have an implementation in the abstract class. Signup and view all the answers

Study Notes

Default Constructors

Default constructors are parameterless.
They set numeric fields to 0.
They set boolean fields to false.
They set character fields to Unicode 0.
They set string fields to null.
They set object fields to null.
Default constructors are public when the class is public.
Default constructors are private when the class is private.
Default constructors are protected when the class is abstract.
Default constructors are internal when the class is internal.

Method Return Types

A method with a return type of void cannot return anything.

Valid Identifiers

_age is a valid identifier.
age is a valid identifier.
age_ is a valid identifier.

Switch Statements

The break keyword prevents falling through a switch case.
The break statement stops execution from falling through to the next matching case expressions.
The default keyword executes a sequence of statements when the switch expressions do not match any of the case statements.
The default keyword sets the default of a parameter to a default value when no value is passed.
The case keyword represents a value that the switch expression could match.

Method Body

In C#, the body of a method is everything between the curly braces.

Overridden Methods

Overridden methods in child classes must have the same name, return type, visibility & parameter list as the method in the parent class.

Methods in Child Classes

Methods in child classes can be accessed by the same class and any child classes.

Abstract Classes and Interfaces

Abstract classes can contain both abstract and non-abstract methods.
Interfaces can only contain abstract methods.
Neither abstract classes nor interfaces can be instantiated in C#.

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Description

Test your knowledge on default constructors, method return types, valid identifiers, and switch statements in Java. This quiz covers fundamental concepts that are essential for understanding how to write effective Java code.