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methods

Interview question Video Tutorial Discussion

A method in Java is a block of code within a class that performs a specific task when called. Methods can accept parameters, execute instructions, and optionally return a result. They help organize code into reusable, manageable units, making programs more modular, readable, and easier to maintain.

Syntax:

access_modifier return_type methodName(parameters) {
    // Method body
}

Example:

public void helloWorld(int a) {
    // code
}

Parameters in Methods

A parameter is a variable listed inside the parentheses in the method definition. It acts as a placeholder for the value you want to pass to the method.

Example:

public class Main {
    public static void main(String[] args) {
        String name = "Quipo House";
        message(name); // 'name' is the argument
    }
    static void message(String name) { // 'name' is the parameter
        System.out.println(name);
    }
}

Output:

Quipo House

Arguments

An argument is the actual value that gets passed to the method’s parameter when the method is called.

Example:

public class Main {
    public static void main(String[] args) {
        message("HELLO QUIPO HOUSE"); // "HELLO QUIPO HOUSE" is the argument
    }
    static void message(String message) {
        System.out.println(message);
    }
}

Output:

HELLO QUIPO HOUSE

Types of Methods in Java

1. Predefined Methods (Built-in Methods)

These are methods already provided by Java libraries. You use them without having to define their logic.

Example:

public class Main {
    public static void main(String[] args) {
        String name = "QUIPO HOUSE";
        System.out.println(name.toLowerCase()); // toLowerCase() is a predefined method
    }
}

Other examples include Math.max(), Math.min(), System.out.println(), etc.

2. User-Defined Methods

These are methods written by the programmer to perform specific tasks.

Example:

public class Main {
    public static void main(String[] args) {
        String name = "Quipo House";
        message(name);
    }

    static void message(String name) {
        System.out.println(name);
    }
}

Output:

Quipo House

3. Static Methods

A static method belongs to the class rather than to any specific object. You can call a static method directly using the class name or from another static method.

Example:

public class Main {
    public static void main(String[] args) {
        String name = "Quipo House";
        message(name);         // Direct call
        Main.message(name);    // Call using class name
        Main m = new Main();
        m.message(name);       // Call using object
    }

    static void message(String name) {
        System.out.println(name);
    }
}

Output:

Quipo House
Quipo House
Quipo House

4. Instance Methods

Also known as non-static methods, these require you to create an object of the class to call them.

Example:

public class Main {
    public static void main(String[] args) {
        InstanceMethod obj = new InstanceMethod();
        obj.displayMessage("HELLO QUIPO HOUSE");
    }
}

class InstanceMethod {
    public void displayMessage(String message) {
        System.out.println(message);
    }
}

Output:

HELLO QUIPO HOUSE

5. Abstract Methods

An abstract method is declared without a body and is marked with the abstract keyword. It must be implemented by subclasses of the abstract class.

Syntax:

abstract void methodName();

Example:

abstract class Message {
    abstract void greet();

    void displayName() {
        System.out.print("QUIPO HOUSE");
    }
}

class Greet extends Message {
    void greet() {
        System.out.print("HELLO ");
    }
}

public class Main {
    public static void main(String[] args) {
        Greet obj = new Greet();
        obj.greet();
        obj.displayName();
    }
}

Output:

HELLO QUIPO HOUSE

Key Points

Methods enhance code reusability and maintainability.

Static methods belong to the class and can be called without creating an object.

Instance methods require an object to be called.

Abstract methods provide a blueprint for subclasses, enforcing implementation.

Tips: Use methods to keep your code modular, readable, and easy to maintain. Choose the appropriate type of method based on your use case and design requirements.