Java Class Methods

Welcome to The Coding College! In this article, we’ll cover class methods in Java, which are essential for defining the behavior of objects and enabling code reusability in programs. By the end, you’ll understand how to create and use methods effectively in your Java applications.

What Are Methods in Java?

In Java, a method is a block of code that performs a specific task. Methods are used to:

• Define behaviors of objects.
• Avoid code repetition (reuse logic).
• Improve code readability and organization.

Syntax of a Method

returnType methodName(parameters) {
    // Method body
    // Perform tasks
    return value; // Optional (only for non-void return types)
}

Components of a Method:

1. Return Type: The data type of the value the method returns (void if it doesn’t return anything).
2. Method Name: The name used to call the method.
3. Parameters: Input values (optional) passed to the method.
4. Method Body: The code logic executed when the method is called.

Example: Defining and Calling a Method

class Calculator {
    // Method to add two numbers
    int addNumbers(int num1, int num2) {
        return num1 + num2;
    }
}

public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator(); // Create an object
        int result = calc.addNumbers(5, 10); // Call the method
        System.out.println("Sum: " + result); // Print the result
    }
}

Output:

Sum: 15

Types of Methods

1. Instance Methods

• Belong to an instance (object) of the class.
• Require an object to call them.

Example:

class Greeting {
    void sayHello() {
        System.out.println("Hello!");
    }
}

public class Main {
    public static void main(String[] args) {
        Greeting greet = new Greeting();
        greet.sayHello();
    }
}

2. Static Methods

• Belong to the class, not any specific object.
• Can be called without creating an object.

Example:

class MathOperations {
    static int multiply(int a, int b) {
        return a * b;
    }
}

public class Main {
    public static void main(String[] args) {
        int result = MathOperations.multiply(3, 7); // Static method call
        System.out.println("Product: " + result);
    }
}

Parameters and Arguments

Method with Parameters

Parameters allow methods to accept input values.

void greet(String name) {
    System.out.println("Hello, " + name + "!");
}

Calling the Method with Arguments

greet("Alice");

Output:

Hello, Alice!

Return Values

Method with a Return Value

int square(int number) {
    return number * number;
}

Using the Return Value

int result = square(4);
System.out.println("Square: " + result);

Output:

Square: 16

Method Overloading

Method overloading allows multiple methods with the same name but different parameters.

Example:

class MathUtils {
    // Overloaded methods
    int add(int a, int b) {
        return a + b;
    }

    double add(double a, double b) {
        return a + b;
    }
}

public class Main {
    public static void main(String[] args) {
        MathUtils math = new MathUtils();
        System.out.println("Integer Sum: " + math.add(5, 10));
        System.out.println("Double Sum: " + math.add(5.5, 10.5));
    }
}

Output:

Integer Sum: 15  
Double Sum: 16.0

Best Practices for Methods

• Use Meaningful Names: Method names should clearly indicate their purpose.

void calculateTotal(); // Clear purpose

• Keep Methods Short: Break complex logic into smaller, manageable methods.
• Avoid Redundancy: Reuse methods wherever possible.
• Document Methods: Use comments or Javadoc to describe the method’s behavior.
• Use Static Methods Wisely: Limit static methods to utility functions when possible.

Practice Problems

1. Create a Student class with methods to calculate the total and percentage of marks.
2. Design a BankAccount class with methods for deposit, withdrawal, and balance check.
3. Write a Shape class with methods to calculate the area of a rectangle and a circle.

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