Java Programming Concepts Quiz

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Questions and Answers

Which method is used to combine two strings in Java?

concat() (correct)

append()

concatenate()

join()

What is the purpose of the `charAt()` method in Java?

To determine the length of a string.

To retrieve a specific character from a string based on its position. (correct)

To convert a string to uppercase.

To remove characters from a string based on their index.

How is a character's position within a string represented in Java?

Using a character code.

As a positive integer starting from 0. (correct)

Using a string literal.

As a negative integer starting from -1.

Which of the following Java statements correctly retrieves the character at index 2 from a string named 'myString'?

char character = myString.charAt(2); Signup and view all the answers

Which of the following code snippets demonstrates the correct usage of the `concat()` method in Java?

<code>String result = "Hello ".concat("World");</code> Signup and view all the answers

What must be true about a constructor in a class?

Its name must match the class name. Signup and view all the answers

When is a constructor invoked?

When the object is created. Signup and view all the answers

Which of the following statements about constructors is incorrect?

A constructor has a different name from its class. Signup and view all the answers

Which feature is NOT allowed for a constructor?

To return a value. Signup and view all the answers

How does a constructor differ from a regular method?

It is not called directly by the user. Signup and view all the answers

What does the term 'immutable' refer to in programming languages like Java?

A data type that is unmodifiable once created Signup and view all the answers

Which of the following is the characteristic feature of Java Strings due to their immutable nature?

Any modification creates a new String object Signup and view all the answers

In the provided example, what will be the effect of reassigning the value of 'example'?

'example' will refer to a new String while the old one is left intact Signup and view all the answers

What does the abs(x) method return?

The positive value of x Signup and view all the answers

Why is immutability considered beneficial in programming?

It allows for easier debugging and improves code efficiency Signup and view all the answers

What will the output of the following code be?

String example = "Hello!";
example = example.concat(" World");
System.out.print(example);

Hello!World Signup and view all the answers

How can a string be declared using the new operator in Java?

String example = new String("Hello!"); Signup and view all the answers

Which group do access modifiers fall under?

Access Modifiers Signup and view all the answers

What is the result of concatenating two immutable strings in Java?

A new string is created with the combined values Signup and view all the answers

What is the primary purpose of the Math class in Java?

To provide mathematical functions and constants Signup and view all the answers

What is the method used to concatenate two strings in Java?

concat() Signup and view all the answers

How are Java modifiers categorized?

Access and Non-Access Signup and view all the answers

What would happen if you called `example.concat(

Hello! Signup and view all the answers

Which of the following is NOT an access modifier in Java?

static Signup and view all the answers

Which of the following statements about strings in Java is incorrect?

Strings are mutable. Signup and view all the answers

In the provided code, what is the primary data structure used to store the `Room` objects?

List Signup and view all the answers

What is the purpose of the `getRooms()` method?

To retrieve the list of <code>Room</code> objects Signup and view all the answers

Which of the following statements is TRUE about the `Room` class in the provided code?

It defines a constructor that takes a String argument Signup and view all the answers

In the context of the code, what does the term 'Has-A' relationship generally refer to?

A relationship where one class has an instance of another class as its member Signup and view all the answers

What is the primary benefit of using a `List` to store the `Room` objects, instead of using individual variables?

It makes it easier to manage the rooms, such as adding or removing them Signup and view all the answers

Study Notes

Object Oriented Programming (OOP) Course Notes

This course covers Object-Oriented Programming (OOP) concepts using Java.
The recommended textbook is Java How to Program by Deitel & Deitel (9th Edition or 6th+ editions are acceptable).
The course includes lectures on OOP history, concepts, and related Java applications.

Lecture 1

OOP History: Alan Kay is considered a father of OOP concepts.
OOP Concept: OOP uses "Objects" and their interactions to design applications and programs. This is a programming paradigm. OOP is an approach to program organization and development.
Decomposition into Objects: OOP breaks a problem into entities called Objects, then builds Attributes (data/variables) and Methods (functions) around these entities.
Problem vs. Solution Space: The program's problem space exists in the real world. The solution space for the program is on the computer.
Object-Oriented Approach: Describe the problem in real-world terms, not in computer program terms.

Lecture 2

Basic Structure of a Java Program: Every Java program needs at least one class. Each line of code must be inside a class. The class keyword introduces a class declaration, followed by the class name.
General Syntax of Java Classes: class Name { // Attributes // Methods public static void main(String args[]) { //some statements } } The filename must match the class name and end with .java.
Java Classes/Objects: Use the class keyword to define a Java class. An object is instance of a class. Classes are templates used to create multiple objects.
Java Class Attributes: Attributes in a class are variables. Example in a class named "Main" with attributes int x; and int y;.
Access to Attributes: Get attributes of a class by creating an object and using the dot syntax: myObj.x. You can set values of attributes as well.
Java Constructor: A special method used for initializing objects, the constructor's name must match the class name and has no return type. All classes have a constructor, if you do not create one Java creates it for you.
Java Packages: Packages in Java group related classes. The Java API is a library of pre-written classes, libraries in Java are divided into packages and classes. Import specific classes or packages (import java.util.Scanner;).

Lecture 3

Java Methods: A method is a block of code run when called. Methods can take parameters (data/information). In OOP, methods/functions are used to perform specific actions.
Why Use Methods for Code Re-use: Methods allow the re-use of code. Define the code once and use it many times.
Method Requirements: Declared inside a class. Use method name, parentheses (())
Java Methods Example: Inside a class Box use methods like void volume() to calculate the volume of a box using its member variables.

Lecture 4

Java Modifiers: Modifiers control access to attributes and methods within a class (access modifiers). Modifiers also specify additional functional behavior (non-access modifiers). For example static indicates class-level not object-level and final indicates a class cannot be inherited.
Access Modifiers (Example):
- public: Accessible from any class.
- default: Accessible only within the same package.
Non-Access Modifiers(Example):
- static: Belongs to class level not object level. Can be called without creating an object.
- final: Prevents inheritance.

Lecture 5

Basic Concepts: Encapsulation, Abstraction, Inheritance, Polymorphism.
Encapsulation: The process of restricting access to data members and methods, allowing control.
Abstraction: Show only essential details to the user and hide others.
Getters (Accessors): Public methods to access private attributes (data).
Setters (Mutators): Public methods to modify private attributes.

Lecture 6

Java Abstraction: Hiding non-essential details of an implementation and only showing essential aspects for a user. Achieved using Interfaces or Abstract classes.
Abstract Classes: Cannot create objects and use the abstract keyword for methods / functions without implementation. The methods need to be implemented in subclasses.
Interfaces: Completely abstract classes used for methods grouping. Use implements. Interfaces can be implemented by multiple subclasses.

Lecture 7

Inheritance: A relationship between classes where a subclass "inherits from" a superclass. The child class adopts attributes/methods from the parent class. Example: class Student extends Person { ... }
Polymorphism: Creates many forms of a method that are related to each other but behave differently depending on which class object is calling it. For example, a print method in different classes will give different output.

Lecture 8

Java Inheritance and multiple inheritance: Java does not support multiple inheritance directly. It is done through interfaces instead which results in fewer complexities.
Super Method: When child class method overrides inherited method, you can access the method from the parent class using super.

Lecture 9

Java Files: Java provides a File class which is used to handle files and directories. Using this class, you can check for files, make files or directories, and read/write files. Use of java.io and related exceptions often help with file handling.
Create a File (example): File myFile = new File("myFile.txt").
Delete a File (example): if(myFile.delete()) { ... }
Write to a File (example): Use the PrintWriter class to write text data to a file.
Read from a File (example): Use the Scanner class to read text data from a file and it will print the output to the console.

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Description

Test your knowledge on Java programming concepts including string manipulation, constructors, and immutability. This quiz covers key methods and features of the Java language to assess your understanding of fundamental principles. Prepare to challenge your Java skills and see how well you know this versatile programming language.