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Lab 4: Java Fundamentals - Operators, Control Flow, Classes, and Arrays

Table of Contents

  1. Introduction
  2. Topic Explanations
  3. Progressive Tasks
  4. Practice Tasks

Introduction

This lab covers fundamental Java concepts including operators, control flow structures, object-oriented programming basics, and array manipulation. Each task builds upon the previous one, creating a comprehensive understanding of Java programming fundamentals.

Topic Explanations

1. Logical and Relational Operators

What are Logical and Relational Operators?

  • Relational Operators: Compare two values and return a boolean result (true or false)

    • == (equal to)
    • != (not equal to)
    • > (greater than)
    • < (less than)
    • >= (greater than or equal to)
    • <= (less than or equal to)

  • Logical Operators: Combine or modify boolean expressions

    • && (AND) - returns true if both conditions are true
    • || (OR) - returns true if at least one condition is true
    • ! (NOT) - reverses the boolean value

How to use:

int a = 5, b = 10;
boolean result1 = a < b;        // true
boolean result2 = a == b;       // false
boolean result3 = (a < b) && (a > 0);  // true
boolean result4 = (a > b) || (a < 0);  // false

Example:

int age = 20;
if (age >= 18 && age <= 65) {
    System.out.println("Working age");
}

2. Basic Data Types

What are Basic Data Types? Java has primitive data types that store simple values:

  • byte (8-bit integer)
  • short (16-bit integer)
  • int (32-bit integer)
  • long (64-bit integer)
  • float (32-bit floating point)
  • double (64-bit floating point)
  • char (16-bit Unicode character)
  • boolean (true or false)

How to use:

int number = 42;
double price = 19.99;
char grade = 'A';
boolean isActive = true;

Example:

int studentId = 12345;
double gpa = 3.75;
char letterGrade = 'B';
boolean isGraduated = false;

3. String Handling

What is String Handling? Strings in Java are objects (not primitives) that represent sequences of characters. The String class provides many methods for manipulating strings.

How to use:

String str = "Hello";
int length = str.length();                    // 5
String upper = str.toUpperCase();             // "HELLO"
String lower = str.toLowerCase();             // "hello"
boolean contains = str.contains("ell");       // true
String substring = str.substring(1, 4);       // "ell"
String concat = str.concat(" World");         // "Hello World"
boolean equals = str.equals("Hello");         // true

Example:

String name = "John Doe";
System.out.println("Length: " + name.length());
System.out.println("First name: " + name.substring(0, 4));
System.out.println("Uppercase: " + name.toUpperCase());

4. Break and Continue Statements

What are Break and Continue?

  • break: Exits the loop immediately
  • continue: Skips the current iteration and continues with the next iteration

How to use:

// break example
for (int i = 0; i < 10; i++) {
    if (i == 5) {
        break;  // exits loop when i is 5
    }
    System.out.println(i);
}

// continue example
for (int i = 0; i < 10; i++) {
    if (i % 2 == 0) {
        continue;  // skips even numbers
    }
    System.out.println(i);
}

Example:

// Find first number divisible by 7
for (int i = 1; i <= 100; i++) {
    if (i % 7 == 0) {
        System.out.println("Found: " + i);
        break;
    }
}

5. For-Each Loop (Enhanced For Loop)

What is For-Each Loop? A simplified loop syntax for iterating through arrays and collections without using index variables.

How to use:

int[] numbers = {1, 2, 3, 4, 5};
for (int num : numbers) {
    System.out.println(num);
}

Example:

String[] names = {"Alice", "Bob", "Charlie"};
for (String name : names) {
    System.out.println("Hello, " + name);
}

6. If/Else/Switch Statements

What are If/Else/Switch? Control flow structures that allow conditional execution of code:

  • if/else: Executes code based on boolean conditions
  • switch: Executes code based on matching a value

How to use:

// if/else
int score = 85;
if (score >= 90) {
    System.out.println("Grade: A");
} else if (score >= 80) {
    System.out.println("Grade: B");
} else {
    System.out.println("Grade: C");
}

// switch
int day = 3;
switch (day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    default:
        System.out.println("Other day");
}

Example:

char operation = '+';
int a = 10, b = 5;
switch (operation) {
    case '+':
        System.out.println(a + b);
        break;
    case '-':
        System.out.println(a - b);
        break;
    case '*':
        System.out.println(a * b);
        break;
    default:
        System.out.println("Invalid operation");
}

7. Constructors

What is a Constructor? A special method that is called when an object is created. It initializes the object's state.

How to use:

public class Student {
    private String name;
    private int age;
    
    // Default constructor
    public Student() {
        name = "Unknown";
        age = 0;
    }
    
    // Parameterized constructor
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

Example:

Student s1 = new Student();              // Uses default constructor
Student s2 = new Student("John", 20);    // Uses parameterized constructor

8. Methods

What are Methods? Blocks of code that perform specific tasks. Methods can take parameters and return values.

How to use:

public class Calculator {
    // Method with parameters and return value
    public int add(int a, int b) {
        return a + b;
    }
    
    // Method without return value (void)
    public void displayMessage(String msg) {
        System.out.println(msg);
    }
}

Example:

Calculator calc = new Calculator();
int result = calc.add(5, 3);  // result = 8
calc.displayMessage("Calculation complete");

9. Method Overloading

What is Method Overloading? Defining multiple methods with the same name but different parameters (different number or types).

How to use:

public class MathUtils {
    public int add(int a, int b) {
        return a + b;
    }
    
    public int add(int a, int b, int c) {
        return a + b + c;
    }
    
    public double add(double a, double b) {
        return a + b;
    }
}

Example:

MathUtils utils = new MathUtils();
int sum1 = utils.add(2, 3);           // Calls first method
int sum2 = utils.add(2, 3, 4);        // Calls second method
double sum3 = utils.add(2.5, 3.5);    // Calls third method

10. Objects

What are Objects? Instances of classes that contain data (attributes) and behavior (methods).

How to use:

// Class definition
public class Car {
    String brand;
    String color;
    
    public void start() {
        System.out.println("Car started");
    }
}

// Creating and using objects
Car myCar = new Car();
myCar.brand = "Toyota";
myCar.color = "Red";
myCar.start();

Example:

Car car1 = new Car();
car1.brand = "Honda";
Car car2 = new Car();
car2.brand = "Ford";

11. Private Attributes

What are Private Attributes? Class attributes marked with private keyword that can only be accessed within the same class, not from outside.

How to use:

public class BankAccount {
    private double balance;  // Private attribute
    
    public void deposit(double amount) {
        balance += amount;  // Can access within class
    }
}

Example:

BankAccount account = new BankAccount();
// account.balance = 1000;  // ERROR: Cannot access private attribute
account.deposit(1000);  // Must use public method

12. Getter and Setter Methods

What are Getters and Setters? Public methods used to access (get) and modify (set) private attributes.

How to use:

public class Person {
    private String name;
    private int age;
    
    // Getter methods
    public String getName() {
        return name;
    }
    
    public int getAge() {
        return age;
    }
    
    // Setter methods
    public void setName(String name) {
        this.name = name;
    }
    
    public void setAge(int age) {
        this.age = age;
    }
}

Example:

Person person = new Person();
person.setName("Alice");
person.setAge(25);
System.out.println(person.getName());  // "Alice"
System.out.println(person.getAge());   // 25

13. Class and Main Class - Calling Methods from Other Classes

What is the difference?

  • Regular Class: Contains attributes and methods for a specific purpose
  • Main Class: Contains the main method, which is the entry point of the program. It can create objects of other classes and call their methods.

How to use:

// Student.java - Regular class
public class Student {
    private String name;
    
    public void displayInfo() {
        System.out.println("Student: " + name);
    }
}

// Main.java - Main class
public class Main {
    public static void main(String[] args) {
        Student student = new Student();
        student.displayInfo();  // Calling method from Student class
    }
}

Example:

// Calculator.java
public class Calculator {
    public int multiply(int a, int b) {
        return a * b;
    }
}

// Main.java
public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator();
        int result = calc.multiply(5, 4);
        System.out.println("Result: " + result);
    }
}

14. This Keyword (Basic)

What is the 'this' keyword? A reference to the current object. It's used to distinguish between instance variables and parameters with the same name.

How to use:

public class Student {
    private String name;
    
    public void setName(String name) {
        this.name = name;  // 'this.name' refers to instance variable
    }
    
    public String getName() {
        return this.name;  // Optional but clear
    }
}

Example:

public class Rectangle {
    private int width;
    private int height;
    
    public Rectangle(int width, int height) {
        this.width = width;    // Instance variable
        this.height = height;  // Instance variable
    }
}

15. Type Conversion and Casting

What is Type Conversion and Casting?

  • Automatic Conversion (Widening): Converting smaller types to larger types (e.g., int to double)
  • Explicit Casting (Narrowing): Converting larger types to smaller types using cast operator

How to use:

// Automatic conversion
int num = 10;
double decimal = num;  // Automatically converts int to double

// Explicit casting
double price = 19.99;
int roundedPrice = (int) price;  // Casts double to int (19)

// Char to int
char letter = 'A';
int ascii = (int) letter;  // 65

Example:

int a = 10;
double b = a;           // Automatic: 10.0
double c = 15.7;
int d = (int) c;        // Explicit: 15

16. Automatic Type Promotion in Expressions

What is Automatic Type Promotion? Java automatically promotes smaller data types to larger ones in expressions to prevent data loss.

How to use:

byte b = 10;
int i = 20;
long result = b + i;  // byte and int promoted to long

int x = 5;
double y = 2.5;
double result2 = x + y;  // int promoted to double

Example:

byte a = 5;
short b = 10;
int c = 15;
long result = a + b + c;  // All promoted to long

17. Arrays (One Dimension and Multi Dimension)

What are Arrays? Containers that hold multiple values of the same type. Arrays can be one-dimensional or multi-dimensional.

How to use:

// One-dimensional array
int[] numbers = new int[5];
numbers[0] = 10;
numbers[1] = 20;

// Or initialize directly
int[] arr = {1, 2, 3, 4, 5};

// Two-dimensional array
int[][] matrix = new int[3][4];
matrix[0][0] = 1;
matrix[0][1] = 2;

// Or initialize directly
int[][] grid = {{1, 2, 3}, {4, 5, 6}};

Example:

// 1D Array
int[] scores = {85, 90, 78, 92, 88};
System.out.println(scores[0]);  // 85

// 2D Array
int[][] table = {{1, 2}, {3, 4}, {5, 6}};
System.out.println(table[1][0]);  // 3

18. Uneven Multidimensional Arrays

What are Uneven Multidimensional Arrays? Multi-dimensional arrays where each row can have a different number of columns.

How to use:

int[][] uneven = new int[3][];
uneven[0] = new int[2];  // First row has 2 columns
uneven[1] = new int[4];  // Second row has 4 columns
uneven[2] = new int[3];  // Third row has 3 columns

// Or initialize directly
int[][] jagged = {
    {1, 2},
    {3, 4, 5, 6},
    {7, 8, 9}
};

Example:

String[][] names = {
    {"Alice", "Bob"},
    {"Charlie", "David", "Eve"},
    {"Frank"}
};

for (int i = 0; i < names.length; i++) {
    for (int j = 0; j < names[i].length; j++) {
        System.out.print(names[i][j] + " ");
    }
    System.out.println();
}

19. Ternary Operator

What is the Ternary Operator? A shorthand for if-else statements: condition ? value_if_true : value_if_false

How to use:

int a = 10, b = 20;
int max = (a > b) ? a : b;  // If a > b, max = a, else max = b

String result = (score >= 60) ? "Pass" : "Fail";

Example:

int age = 20;
String status = (age >= 18) ? "Adult" : "Minor";
System.out.println(status);  // "Adult"

20. Returning Array from Method

What is Returning Array from Method? Methods can return arrays as their return type.

How to use:

public class ArrayUtils {
    public int[] createArray(int size) {
        int[] arr = new int[size];
        for (int i = 0; i < size; i++) {
            arr[i] = i * 2;
        }
        return arr;
    }
}

Example:

public int[] getEvenNumbers(int limit) {
    int[] evens = new int[limit / 2];
    int index = 0;
    for (int i = 2; i <= limit; i += 2) {
        evens[index++] = i;
    }
    return evens;
}

21. Passing Array as Parameter

What is Passing Array as Parameter? Arrays can be passed to methods as parameters, and modifications to array elements affect the original array.

How to use:

public class ArrayOperations {
    public void printArray(int[] arr) {
        for (int num : arr) {
            System.out.print(num + " ");
        }
    }
    
    public void modifyArray(int[] arr) {
        arr[0] = 999;  // Modifies original array
    }
}

Example:

public void doubleValues(int[] numbers) {
    for (int i = 0; i < numbers.length; i++) {
        numbers[i] *= 2;  // Modifies original array
    }
}

// Usage
int[] arr = {1, 2, 3, 4, 5};
doubleValues(arr);
// arr is now {2, 4, 6, 8, 10}

Progressive Tasks

Important: Each task builds on the previous one. You will modify the same Student class by adding new methods and features. Create a Main class with a main method to test your Student class.

Task 1: Student Class - Basic Structure

Create a Student class with the following requirements:

Requirements:

  1. Private attributes: name (String), studentId (int), gpa (double)
  2. Default constructor that initializes name to "Unknown", studentId to 0, gpa to 0.0
  3. Parameterized constructor that takes name, studentId, and gpa
  4. Getter methods: getName(), getStudentId(), getGpa()
  5. Setter methods: setName(String name), setStudentId(int studentId), setGpa(double gpa)
  6. A method displayInfo() that prints all student information
  7. Use this keyword appropriately in constructors and setters

Create a Main class to test:

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student();
        Student s2 = new Student("John Doe", 12345, 3.75);
        
        s1.displayInfo();
        s2.displayInfo();
        
        s1.setName("Jane Smith");
        s1.setStudentId(12346);
        s1.setGpa(3.90);
        s1.displayInfo();
    }
}

Expected Output:

Student Information:
Name: Unknown
Student ID: 0
GPA: 0.0

Student Information:
Name: John Doe
Student ID: 12345
GPA: 3.75

Student Information:
Name: Jane Smith
Student ID: 12346
GPA: 3.90

Main.java

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student();
        Student s2 = new Student("John Doe", 12345, 3.75);
        
        s1.displayInfo();
        s2.displayInfo();
        
        s1.setName("Jane Smith");
        s1.setStudentId(12346);
        s1.setGpa(3.90);
        s1.displayInfo();
    }
}

Student.java

class Student {
	
	private String name;
	private int studentId;
	private double gpa;

	Student(){
		name = "Unknown";
		studentId = 0;
		gpa = 0.0;
	}

	Student(String name,int studentId,double gpa){
		this.name = name;
		this.studentId = studentId;
		this.gpa = gpa;
	}

	String getName(){
		return name;
	}
	int getStudentId(){
		return studentId;
	}
	double getGpa(){
		return gpa;
	}
	void setName(String name){
		this.name = name;
	}
	void setStudentId(int studentId){
		this.studentId = studentId;
	}
	void setGpa(double gpa){
		this.gpa = gpa;
	}

	void displayInfo(){
		System.out.println("Student Information:");
		System.out.println("Student Name : " + name);
		System.out.println("Student ID : " + studentId);
		System.out.println("Student GPA : " + gpa);
		System.out.println();
	}

}

Task 2: Add Control Flow Methods

Modify your Student class from Task 1 by adding the following methods:

Requirements:

  1. Method calculateGrade() that returns a char based on GPA using if/else:
    • 'A' if gpa >= 3.7
    • 'B' if gpa >= 3.0
    • 'C' if gpa >= 2.0
    • 'D' if gpa >= 1.0
    • 'F' otherwise
  2. Method getGradeLetter() that returns the grade letter using switch statement
  3. Method isHonorStudent() that returns true if GPA >= 3.5 (use ternary operator)
  4. Method updateGPA(double newGPA) that updates the GPA and validates it's between 0.0 and 4.0 using if/else
  5. Method getStatus() that returns "Excellent", "Good", "Average", or "Needs Improvement" based on GPA using if/else

Update your Main class:

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        Student s2 = new Student("Jane Smith", 12346, 2.50);
        
        System.out.println("Grade: " + s1.calculateGrade());
        System.out.println("Is Honor Student: " + s1.isHonorStudent());
        System.out.println("Status: " + s1.getStatus());
        
        s2.updateGPA(3.90);
        s2.displayInfo();
    }
}

Expected Output:

Grade: B
Is Honor Student: true
Status: Good
Student Information:
Name: Jane Smith
Student ID: 12346
GPA: 3.90

class Student {
	
	private String name;
	private int studentId;
	private double gpa;

	Student(){
		name = "Unknown";
		studentId = 0;
		gpa = 0.0;
	}

	Student(String name,int studentId,double gpa){
		this.name = name;
		this.studentId = studentId;
		this.gpa = gpa;
	}

	String getName(){
		return name;
	}
	int getStudentId(){
		return studentId;
	}
	double getGpa(){
		return gpa;
	}
	void setName(String name){
		this.name = name;
	}
	void setStudentId(int studentId){
		this.studentId = studentId;
	}
	void setGpa(double gpa){
		this.gpa = gpa;
	}

	void displayInfo(){
		System.out.println("Student Information:");
		System.out.println("Student Name : " + name);
		System.out.println("Student ID : " + studentId);
		System.out.println("Student GPA : " + gpa);
		System.out.println();
	}

	char calculateGrade(){
		if(gpa >= 3.7) return 'A';
		else if (gpa >= 3) return 'B';
		else if (gpa >= 2) return 'C';
		else if (gpa >= 1) return 'D';
		else return 'F';
    }
	String getGradeLetter(){
		int level = 0;

		if (gpa >= 3.7) level = 4;
		else if (gpa >= 3) level = 3;
		else if (gpa >= 2) level = 2;
		else if (gpa >= 1) level = 1;

		switch(level){
		case 4:
			return "A";
		case 3:
			return "B";
		case 2:
			return "C";
		case 1:
			return "D";
		default:
			return "F";
		}
	}

	boolean isHonorStudent(){
		return (gpa > 3.5 ) ? true : false;
	}

	void updateGPA(double newGPA){
		if (newGPA>= 0.0 && newGPA <= 4.0){
			gpa = newGPA;
		}
	}

	String getStatus(){
		if (getGradeLetter().equals("A")) return "Excellent";
		else if (getGradeLetter().equals("B")) return "Good";
		else if (getGradeLetter().equals("C")) return "Average";
		else return "Need Improvements";
	}

}

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        Student s2 = new Student("Jane Smith", 12346, 2.50);
        
        System.out.println("Grade: " + s1.calculateGrade());
        System.out.println("Is Honor Student: " + s1.isHonorStudent());
        System.out.println("Status: " + s1.getStatus());
        
        s2.updateGPA(3.90);
        s2.displayInfo();
    }
}

Task 3: Add String Handling and Array Methods

Modify your Student class from Task 2 by adding the following methods:

Requirements:

  1. Method formatName() that returns the name in "Last, First" format (assume name is "First Last")
    • Use string methods: substring(), indexOf(), toUpperCase(), toLowerCase()
  2. Method getInitials() that returns the initials of the name (e.g., "John Doe" → "JD")
  3. Method validateName() that returns true if name contains only letters and spaces
  4. Method getStudentInfoArray() that returns a String array with [name, studentId as String, gpa as String]
    • Use type conversion to convert int and double to String
  5. Method displayFormattedInfo() that displays information using formatted strings

Update your Main class:

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        
        System.out.println("Formatted Name: " + s1.formatName());
        System.out.println("Initials: " + s1.getInitials());
        System.out.println("Valid Name: " + s1.validateName());
        
        String[] info = s1.getStudentInfoArray();
        for (String data : info) {
            System.out.println(data);
        }
        
        s1.displayFormattedInfo();
    }
}

Expected Output:

Formatted Name: DOE, JOHN
Initials: JD
Valid Name: true
John Doe
12345
3.75
=== Formatted Student Info ===
Name: John Doe | ID: 12345 | GPA: 3.75

class Student {
	
	private String name;
	private int studentId;
	private double gpa; 

	Student(){
		name = "Unknown";
		studentId = 0;
		gpa = 0.0;
	}

	Student(String name,int studentId,double gpa){
		this.name = name;
		this.studentId = studentId;
		this.gpa = gpa;
	}

	String getName(){
		return name;
	}
	int getStudentId(){
		return studentId;
	}
	double getGpa(){
		return gpa;
	}
	void setName(String name){
		this.name = name;
	}
	void setStudentId(int studentId){
		this.studentId = studentId;
	}
	void setGpa(double gpa){
		this.gpa = gpa;
	}

	void displayInfo(){
		System.out.println("Student Information:");
		System.out.println("Student Name : " + name);
		System.out.println("Student ID : " + studentId);
		System.out.println("Student GPA : " + gpa);
		System.out.println();
	}

	char calculateGrade(){
		if(gpa >= 3.7) return 'A';
		else if (gpa >= 3) return 'B';
		else if (gpa >= 2) return 'C';
		else if (gpa >= 1) return 'D';
		else return 'F';
    }
	String getGradeLetter(){
		int level = 0;

		if (gpa >= 3.7) level = 4;
		else if (gpa >= 3) level = 3;
		else if (gpa >= 2) level = 2;
		else if (gpa >= 1) level = 1;

		switch(level){
		case 4:
			return "A";
		case 3:
			return "B";
		case 2:
			return "C";
		case 1:
			return "D";
		default:
			return "F";
		}
	}

	boolean isHonorStudent(){
		return (gpa > 3.5 ) ? true : false;
	}

	void updateGPA(double newGPA){
		if (newGPA>= 0.0 && newGPA <= 4.0){
			gpa = newGPA;
		}
	}

	String getStatus(){
		if (getGradeLetter().equals("A")) return "Excellent";
		else if (getGradeLetter().equals("B")) return "Good";
		else if (getGradeLetter().equals("C")) return "Average";
		else return "Need Improvements";
	}

	String formatName(){
		int spaceIndex = name.indexOf(" ");
		if (spaceIndex == -1) return name;
		String firstName = name.substring(0 , spaceIndex);
		String lastName = name.substring(spaceIndex + 1);

		firstName = firstName.substring(0,1).toUpperCase() + firstName.substring(1).toLowerCase();
		lastName = lastName.substring(0,1).toUpperCase() + lastName.substring(1).toLowerCase();

		return lastName + "," + firstName;

	}

	String getInitials() {
    int spaceIndex = name.indexOf(" ");
    String firstName = spaceIndex != -1 ? name.substring(0, spaceIndex) : name;
    String lastName = spaceIndex != -1 ? name.substring(spaceIndex + 1) : "";

    String initials = firstName.substring(0,1).toUpperCase();
    if (!lastName.isEmpty()) {
        initials += lastName.substring(0,1).toUpperCase();
    }

    return initials;
    }

    boolean validateName(){
    	return name.matches("[A-Za-z ]+");

    }

    String[] getStudentInfoArray() {
    String[] info = new String[3];
    info[0] = name;
    info[1] = String.valueOf(studentId);
    info[2] = String.valueOf(gpa);
    return info;
    }

    void displayFormattedInfo() {
    System.out.println("=== Formatted Student Info ===");
    System.out.println(
        String.format("Name: %s | ID: %d | GPA: %.2f", name, studentId, gpa)
    );
    
    }
    
}

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        
        System.out.println("Formatted Name: " + s1.formatName());
        System.out.println("Initials: " + s1.getInitials());
        System.out.println("Valid Name: " + s1.validateName());
        
        String[] info = s1.getStudentInfoArray();
        for (String data : info) {
            System.out.println(data);
        }
        
        s1.displayFormattedInfo();
    }

Task 4: Add Array Processing Methods

Modify your Student class from Task 3 by adding the following methods that work with arrays:

Requirements:

  1. Method processGPAs(double[] gpas) that takes an array of GPAs and:
    • Uses for-each loop to find the highest GPA
    • Uses break when a GPA > 4.0 is found (invalid)
    • Uses continue to skip GPAs < 1.0
    • Returns the highest valid GPA
  2. Method calculateAverage(double[] grades) that calculates and returns the average of an array
  3. Method findGradeInArray(char[] grades, char target) that searches for a grade in an array:
    • Uses break when found
    • Returns true if found, false otherwise
  4. Method getGradeArray(int count) that returns an array of grade characters (A, B, C, D, F) based on count
    • Use switch or if/else to assign grades
  5. Method modifyArray(int[] numbers) that doubles all values in the array (pass array as parameter)

Update your Main class:

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        
        double[] gpas = {3.5, 2.8, 4.0, 3.9, 0.5};
        double highest = s1.processGPAs(gpas);
        System.out.println("Highest GPA: " + highest);
        
        double[] grades = {85.0, 90.0, 78.0, 92.0};
        double avg = s1.calculateAverage(grades);
        System.out.println("Average: " + avg);
        
        char[] gradeList = {'A', 'B', 'C', 'A', 'B'};
        boolean found = s1.findGradeInArray(gradeList, 'A');
        System.out.println("Grade A found: " + found);
        
        int[] nums = {1, 2, 3, 4, 5};
        s1.modifyArray(nums);
        for (int num : nums) {
            System.out.print(num + " ");
        }
    }
}

Expected Output:

Highest GPA: 4.0
Average: 86.25
Grade A found: true
2 4 6 8 10

class Student {
	
	private String name;
	private int studentId;
	private double gpa;

	Student(){
		name = "Unknown";
		studentId = 0;
		gpa = 0.0;
	}

	Student(String name,int studentId,double gpa){
		this.name = name;
		this.studentId = studentId;
		this.gpa = gpa;
	}

	String getName(){
		return name;
	}
	int getStudentId(){
		return studentId;
	}
	double getGpa(){
		return gpa;
	}
	void setName(String name){
		this.name = name;
	}
	void setStudentId(int studentId){
		this.studentId = studentId;
	}
	void setGpa(double gpa){
		this.gpa = gpa;
	}

	void displayInfo(){
		System.out.println("Student Information:");
		System.out.println("Student Name : " + name);
		System.out.println("Student ID : " + studentId);
		System.out.println("Student GPA : " + gpa);
		System.out.println();
	}

	char calculateGrade(){
		if(gpa >= 3.7) return 'A';
		else if (gpa >= 3) return 'B';
		else if (gpa >= 2) return 'C';
		else if (gpa >= 1) return 'D';
		else return 'F';
    }
	String getGradeLetter(){
		int level = 0;

		if (gpa >= 3.7) level = 4;
		else if (gpa >= 3) level = 3;
		else if (gpa >= 2) level = 2;
		else if (gpa >= 1) level = 1;

		switch(level){
		case 4:
			return "A";
		case 3:
			return "B";
		case 2:
			return "C";
		case 1:
			return "D";
		default:
			return "F";
		}
	}

	boolean isHonorStudent(){
		return (gpa > 3.5 ) ? true : false;
	}

	void updateGPA(double newGPA){
		if (newGPA>= 0.0 && newGPA <= 4.0){
			gpa = newGPA;
		}
	}

	String getStatus(){
		if (getGradeLetter().equals("A")) return "Excellent";
		else if (getGradeLetter().equals("B")) return "Good";
		else if (getGradeLetter().equals("C")) return "Average";
		else return "Need Improvements";
	}

	String formatName(){
		int spaceIndex = name.indexOf(" ");
		if (spaceIndex == -1) return name;
		String firstName = name.substring(0 , spaceIndex);
		String lastName = name.substring(spaceIndex + 1);

		firstName = firstName.substring(0,1).toUpperCase() + firstName.substring(1).toLowerCase();
		lastName = lastName.substring(0,1).toUpperCase() + lastName.substring(1).toLowerCase();

		return lastName + "," + firstName;

	}

	String getInitials() {
    int spaceIndex = name.indexOf(" ");
    String firstName = spaceIndex != -1 ? name.substring(0, spaceIndex) : name;
    String lastName = spaceIndex != -1 ? name.substring(spaceIndex + 1) : "";

    String initials = firstName.substring(0,1).toUpperCase();
    if (!lastName.isEmpty()) {
        initials += lastName.substring(0,1).toUpperCase();
    }

    return initials;
    }

    boolean validateName(){
    	return name.matches("[A-Za-z ]+");

    }

    String[] getStudentInfoArray() {
    String[] info = new String[3];
    info[0] = name;
    info[1] = String.valueOf(studentId);
    info[2] = String.valueOf(gpa);
    return info;
    }

    void displayFormattedInfo() {
    System.out.println("=== Formatted Student Info ===");
    System.out.println(
        String.format("Name: %s | ID: %d | GPA: %.2f", name, studentId, gpa)
    );
    
    }

    double processGPAs(double[] gpas){
    	double highest = 0;
    	for (double gpa : gpas){
    		if (gpa > 4.0) {
    			break;
    		}
    		if (gpa < 0.0){
    			continue;
    		}
    		if(gpa > highest) highest = gpa;
    	}
    	return highest;
    }
    double calculateAverage(double[] grades){
    	double average = 0.0;
    	double sum = 0;
    	for (double grade : grades){
    		sum = grade + sum;
    	}
    	average = sum / grades.length;
    	return average;
    }
    boolean findGradeInArray(char[] grades, char target){
    	boolean found = false;
    	for (char grade : grades){
    		if (target == grade){
    			found = true;
    			break;
    		}
    	}
    		return found;
    }
    void modifyArray(int[] numbers){
    	for (int i=0; i<numbers.length; i++){
    		numbers[i] = 2 * numbers[i];
    	}
    }

}
public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        
        double[] gpas = {3.5, 2.8, 4.0, 3.9, 0.5};
        double highest = s1.processGPAs(gpas);
        System.out.println("Highest GPA: " + highest);
        
        double[] grades = {85.0, 90.0, 78.0, 92.0};
        double avg = s1.calculateAverage(grades);
        System.out.println("Average: " + avg);
        
        char[] gradeList = {'A', 'B', 'C', 'A', 'B'};
        boolean found = s1.findGradeInArray(gradeList, 'A');
        System.out.println("Grade A found: " + found);
        
        int[] nums = {1, 2, 3, 4, 5};
        s1.modifyArray(nums);
        for (int num : nums) {
            System.out.print(num + " ");
        }
    }
}

Task 5: Add Method Overloading and Multi-dimensional Arrays

Modify your Student class from Task 4 by adding the following methods:

Requirements:

  1. Method Overloading: Create multiple versions of calculateTotal():
    • calculateTotal(int a, int b) - returns int
    • calculateTotal(double a, double b) - returns double
    • calculateTotal(int a, int b, int c) - returns int
  2. Method process2DArray(int[][] matrix) that:
    • Takes a 2D array and finds the maximum value
    • Returns the maximum value
    • Uses nested loops
  3. Method getStudentGrades2D() that returns a 2D array representing grades for multiple assignments:
    • Returns a 3x4 array (3 students, 4 assignments) with sample data
  4. Method displayGradeTable(int[][] grades) that displays grades in table format
  5. Method calculateRowAverage(int[][] grades, int row) that returns average of a specific row
  6. Method calculateColumnAverage(int[][] grades, int col) that returns average of a specific column

Update your Main class:

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        
        // Method overloading
        System.out.println("Sum (int): " + s1.calculateTotal(5, 3));
        System.out.println("Sum (double): " + s1.calculateTotal(5.5, 3.2));
        System.out.println("Sum (3 ints): " + s1.calculateTotal(5, 3, 2));
        
        // 2D Array
        int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
        int max = s1.process2DArray(matrix);
        System.out.println("Max value: " + max);
        
        int[][] grades = s1.getStudentGrades2D();
        s1.displayGradeTable(grades);
        
        double rowAvg = s1.calculateRowAverage(grades, 0);
        System.out.println("Row 0 average: " + rowAvg);
    }
}

Expected Output:

Sum (int): 8
Sum (double): 8.7
Sum (3 ints): 10
Max value: 9
Grade Table:
Student 0: 85 90 88 92
Student 1: 78 82 80 85
Student 2: 92 95 90 93
Row 0 average: 88.75

class Student {
	
	private String name;
	private int studentId;
	private double gpa;

	Student(){
		name = "Unknown";
		studentId = 0;
		gpa = 0.0;
	}

	Student(String name,int studentId,double gpa){
		this.name = name;
		this.studentId = studentId;
		this.gpa = gpa;
	}

	String getName(){
		return name;
	}
	int getStudentId(){
		return studentId;
	}
	double getGpa(){
		return gpa;
	}
	void setName(String name){
		this.name = name;
	}
	void setStudentId(int studentId){
		this.studentId = studentId;
	}
	void setGpa(double gpa){
		this.gpa = gpa;
	}

	void displayInfo(){
		System.out.println("Student Information:");
		System.out.println("Student Name : " + name);
		System.out.println("Student ID : " + studentId);
		System.out.println("Student GPA : " + gpa);
		System.out.println();
	}

	char calculateGrade(){
		if(gpa >= 3.7) return 'A';
		else if (gpa >= 3) return 'B';
		else if (gpa >= 2) return 'C';
		else if (gpa >= 1) return 'D';
		else return 'F';
    }
	String getGradeLetter(){
		int level = 0;

		if (gpa >= 3.7) level = 4;
		else if (gpa >= 3) level = 3;
		else if (gpa >= 2) level = 2;
		else if (gpa >= 1) level = 1;

		switch(level){
		case 4:
			return "A";
		case 3:
			return "B";
		case 2:
			return "C";
		case 1:
			return "D";
		default:
			return "F";
		}
	}

	boolean isHonorStudent(){
		return (gpa > 3.5 ) ? true : false;
	}

	void updateGPA(double newGPA){
		if (newGPA>= 0.0 && newGPA <= 4.0){
			gpa = newGPA;
		}
	}

	String getStatus(){
		if (getGradeLetter().equals("A")) return "Excellent";
		else if (getGradeLetter().equals("B")) return "Good";
		else if (getGradeLetter().equals("C")) return "Average";
		else return "Need Improvements";
	}

	String formatName(){
		int spaceIndex = name.indexOf(" ");
		if (spaceIndex == -1) return name;
		String firstName = name.substring(0 , spaceIndex);
		String lastName = name.substring(spaceIndex + 1);

		firstName = firstName.substring(0,1).toUpperCase() + firstName.substring(1).toLowerCase();
		lastName = lastName.substring(0,1).toUpperCase() + lastName.substring(1).toLowerCase();

		return lastName + "," + firstName;

	}

	String getInitials() {
    int spaceIndex = name.indexOf(" ");
    String firstName = spaceIndex != -1 ? name.substring(0, spaceIndex) : name;
    String lastName = spaceIndex != -1 ? name.substring(spaceIndex + 1) : "";

    String initials = firstName.substring(0,1).toUpperCase();
    if (!lastName.isEmpty()) {
        initials += lastName.substring(0,1).toUpperCase();
    }

    return initials;
    }

    boolean validateName(){
    	return name.matches("[A-Za-z ]+");

    }

    String[] getStudentInfoArray() {
    String[] info = new String[3];
    info[0] = name;
    info[1] = String.valueOf(studentId);
    info[2] = String.valueOf(gpa);
    return info;
    }

    void displayFormattedInfo() {
    System.out.println("=== Formatted Student Info ===");
    System.out.println(
        String.format("Name: %s | ID: %d | GPA: %.2f", name, studentId, gpa)
    );
    
    }

    double processGPAs(double[] gpas){
    	double highest = 0;
    	for (double gpa : gpas){
    		if (gpa > 4.0) {
    			break;
    		}
    		if (gpa < 0.0){
    			continue;
    		}
    		if(gpa > highest) highest = gpa;
    	}
    	return highest;
    }
    double calculateAverage(double[] grades){
    	double average = 0.0;
    	double sum = 0;
    	for (double grade : grades){
    		sum = grade + sum;
    	}
    	average = sum / grades.length;
    	return average;
    }
    boolean findGradeInArray(char[] grades, char target){
    	boolean found = false;
    	for (char grade : grades){
    		if (target == grade){
    			found = true;
    			break;
    		}
    	}
    		return found;
    }
    void modifyArray(int[] numbers){
    	for (int i=0; i<numbers.length; i++){
    		numbers[i] = 2 * numbers[i];
    	}
    }
    int calculateTotal(int a, int b){
    	return a+b;
    }
    double calculateTotal(double a, double b){
    	return a+b;
    }
    int calculateTotal(int a, int b, int c){
    	return a+b+c;
    }
    int process2DArray(int[][] matrix){
    	int max = matrix[0][0];
    	for (int i=0; i<matrix.length; i++){
    		for (int j=0; j<matrix[i].length; j++){
    			if (matrix[i][j] > max){
    				max = matrix[i][j];
    			}
    		}
    	}
    	return max;
    }
    int[][] getStudentGrades2D(){
    	int[][] grades = {
    		{67,87,89,64},
    		{76,76,98,83},
    		{83,74,92,59}
    	};
    	return grades;
    }
    void displayGradeTable(int[][] grades){
    	for (int i=0; i<grades.length; i++){
    		System.out.print("Student " + i + ":");
    		for (int j=0; j<grades[i].length; j++){
    			System.out.print(grades[i][j] + " ");
    		}
    		System.out.println();
    	}
    }
    double calculateRowAverage(int[][] grades, int row){
    	int sum = 0;

    	for (int j=0; j<grades[row].length; j++){
    		sum +=  grades[row][j];
    	}
    	return (double)sum/grades[row].length;
    }
    double calculateColumnAverage(int[][] grades, int col){
    	int sum = 0;
    	for (int i=0; i<grades.length; i++){
    		sum += grades[i][col];
    	}
    	return (double)sum/grades.length;
    }

}
public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        
        // Method overloading
        System.out.println("Sum (int): " + s1.calculateTotal(5, 3));
        System.out.println("Sum (double): " + s1.calculateTotal(5.5, 3.2));
        System.out.println("Sum (3 ints): " + s1.calculateTotal(5, 3, 2));
        
        // 2D Array
        int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
        int max = s1.process2DArray(matrix);
        System.out.println("Max value: " + max);
        
        int[][] grades = s1.getStudentGrades2D();
        s1.displayGradeTable(grades);
        
        double rowAvg = s1.calculateRowAverage(grades, 0);
        System.out.println("Row 0 average: " + rowAvg);
    }
}

Task 6: Add Uneven Arrays, Type Conversion, and Complete Integration

Modify your Student class from Task 5 by adding the following final methods:

Requirements:

  1. Method createUnevenArray() that returns an uneven 2D array (jagged array):
    • First row: 2 elements
    • Second row: 4 elements
    • Third row: 3 elements
    • Initialize with sample data
  2. Method displayUnevenArray(int[][] arr) that displays the uneven array
  3. Method convertTypes() that demonstrates type conversion:
    • Convert int to double (automatic)
    • Convert double to int (explicit casting)
    • Convert char to int (explicit casting)
    • Return a String array with conversion results
  4. Method demonstrateTypePromotion() that shows automatic type promotion:
    • Add byte + short + int, store in long
    • Add int + float, store in double
    • Return results as a String
  5. Method completeStudentReport() that creates a comprehensive report:
    • Uses all previous methods
    • Returns a formatted String with all student information
    • Uses string handling, arrays, and all control structures

Update your Main class to demonstrate everything:

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("John Doe", 12345, 3.75);
        Student s2 = new Student("Jane Smith", 12346, 3.90);
        
        // Display complete information
        System.out.println("=== Student 1 ===");
        System.out.println(s1.completeStudentReport());
        
        System.out.println("\n=== Student 2 ===");
        System.out.println(s2.completeStudentReport());
        
        // Demonstrate uneven arrays
        int[][] uneven = s1.createUnevenArray();
        s1.displayUnevenArray(uneven);
        
        // Demonstrate type conversion
        String[] conversions = s1.convertTypes();
        for (String conv : conversions) {
            System.out.println(conv);
        }
        
        // Demonstrate type promotion
        String promotion = s1.demonstrateTypePromotion();
        System.out.println(promotion);
        
        // Array operations
        double[] gpas = {3.5, 3.8, 2.9, 3.95};
        double highest = s1.processGPAs(gpas);
        System.out.println("Highest GPA from array: " + highest);
        
        // Method overloading demonstration
        System.out.println("Overloaded methods:");
        System.out.println(s1.calculateTotal(10, 20));
        System.out.println(s1.calculateTotal(10.5, 20.5));
        System.out.println(s1.calculateTotal(10, 20, 30));
    }
}

Expected Output:

=== Student 1 ===
[Complete formatted report with all information]

=== Student 2 ===
[Complete formatted report with all information]

Uneven Array:
Row 0: 1 2
Row 1: 3 4 5 6
Row 2: 7 8 9

[Type conversion results]
[Type promotion results]
Highest GPA from array: 3.95
Overloaded methods:
30
31.0
60

Practice Tasks

Note: For each practice task, create one class with all methods and a separate Main class with a main method to test it.

Practice Task 1: Calculator Class

Create a Calculator class with:

  • Private attributes: num1 (double), num2 (double)
  • Default constructor and parameterized constructor
  • Getter and setter methods
  • Overloaded methods:
    • add(int a, int b) returns int
    • add(double a, double b) returns double
    • add(int a, int b, int c) returns int
  • Similar overloading for subtract(), multiply(), divide()
  • Method getCalculationHistory() that returns an array of Strings with calculation results
  • Method performOperation(char op) that uses switch statement to perform operations
  • Create a Main class to test all methods

Practice Task 2: Temperature Converter

Create a TemperatureConverter class:

  • Private attribute: temperature (double)
  • Constructors and getters/setters
  • Method celsiusToFahrenheit(double celsius) returns double
  • Method fahrenheitToCelsius(double fahrenheit) returns double
  • Method convertArray(double[] temps, String type) that converts an array of temperatures
  • Method getTemperatureStatus(double temp) that uses ternary operator: returns "Hot" if > 25°C, else "Cold"
  • Method convertWithType(double temp, char type) that uses switch statement:
    • 'C' converts to Fahrenheit
    • 'F' converts to Celsius
  • Create a Main class to test all methods

Practice Task 3: String Analyzer

Create a StringAnalyzer class:

  • Private attribute: text (String)
  • Constructors and getters/setters
  • Method getCharacterFrequency(String str) that returns an int array with frequency of each character
  • Method getVowels(String str) that returns a char array of all vowels found
  • Method reverseString(String str) that returns reversed string
  • Method countWords(String str) that returns number of words
  • Method findSubstring(String str, String sub) that uses break when substring is found
  • Use for-each loop where appropriate
  • Use continue to skip spaces when counting characters
  • Create a Main class to test all methods

Practice Task 4: Matrix Operations

Create a Matrix class:

  • Private attribute: matrix (2D int array)
  • Constructor that takes 2D array to initialize
  • Method addMatrices(int[][] m1, int[][] m2) that returns new matrix (sum of two matrices)
  • Method multiplyByScalar(int scalar) that multiplies the matrix by a number
  • Method findMaximum() that returns maximum value in matrix
  • Method createTriangularMatrix(int size) that returns an uneven 2D array (triangular shape)
  • Method displayMatrix(int[][] m) that displays matrix in formatted way
  • Method getRowSum(int row) that returns sum of a specific row
  • Method getColumnSum(int col) that returns sum of a specific column
  • Create a Main class to test all methods

Practice Task 5: Bank Account System

Create a BankAccount class:

  • Private attributes: accountNumber (int), balance (double), accountType (String)
  • Default constructor and parameterized constructor
  • Getter and setter methods
  • Method deposit(double amount) that adds to balance (use logical operators to validate amount > 0)
  • Method withdraw(double amount) that subtracts from balance (validate amount > 0 and <= balance)
  • Method convertToUSD(double rate) that converts balance using type casting
  • Method getAccountInfoArray() that returns String array with account information
  • Method isAccountValid() that returns true if accountNumber > 0 and balance >= 0 (use logical operators)
  • Method getAccountStatus() that uses ternary operator: "Active" if balance > 0, else "Inactive"
  • Create a Main class to test all methods

Practice Task 6: Number Processor

Create a NumberProcessor class:

  • Private attribute: numbers (int array)
  • Constructor that takes an array
  • Method getStatistics() that returns a double array with:
    • [0] = average
    • [1] = maximum
    • [2] = minimum
    • [3] = sum
  • Method filterEvenNumbers() that returns array of even numbers (use continue to skip odds)
  • Method findNumber(int target) that uses break when number is found, returns index or -1
  • Method sortArray() that sorts the array (simple bubble sort)
  • Method convertToDoubleArray() that returns double array (demonstrates type conversion)
  • Method createMultiplicationTable(int n) that returns 2D array (n x n multiplication table)
  • Method displayTable(int[][] table) that displays table using string formatting
  • Use all operators, control structures, and array operations learned
  • Create a Main class to test all methods

Submission Guidelines

  1. Complete all progressive tasks (Task 1-6)
  2. Complete at least 3 practice tasks
  3. Ensure all code compiles without errors
  4. Include comments explaining complex logic
  5. Test all methods with different inputs
  6. Submit one word file on elearning portal as discussed format

Notes

  • Important Structure:
    • Create ONE class (e.g., Student) with all methods, constructors, getters, setters, and attributes
    • Create a separate Main class with a main method to test your class
    • Each task MODIFIES the same class by adding new methods - do not create new classes
  • Each task builds upon the previous one, so make sure Task 1 works correctly before moving to Task 2
  • When adding new methods in later tasks, keep all previous methods from earlier tasks
  • Use meaningful variable and method names
  • Follow Java naming conventions (camelCase for methods/variables, PascalCase for classes)
  • Test your code with different inputs to ensure it works correctly
  • Pay attention to array bounds to avoid ArrayIndexOutOfBoundsException
  • In the Main class, create objects of your class and call methods to demonstrate functionality