Methods in JAVA

In Java, a method is a block of code that performs a specific task or function. Methods are an essential part of any Java program as they help break down complex code into smaller, more manageable pieces. They provide structure, reusability, and modularity to your code, making it easier to understand and maintain.

Method Syntax

To define a method in Java, you need to follow a specific syntax:

access_modifier return_type method_name(parameter_list) { // Method body // Perform tasks here }

Let's break down the components of this syntax:

access_modifier: This specifies the visibility of the method, which can be "public," "private," "protected," or package-private.

return_type: It defines the data type of the value that the method returns. If a method doesn't return any value, you use the keyword "void."

method_name: This is a user-defined identifier for your method.

parameter_list: It contains variables that the method accepts as input.

Method Examples

Let's illustrate this with a simple example. Suppose you want to create a method that adds two integers and returns the result:

public int add(int num1, int num2) { return num1 + num2; }

In this example:

The method is named "add."

It takes two integer parameters, num1 and num2.

It returns the sum of the two numbers.

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Types of methods in JAVA

There are mainly two types of methods available in java

1) Pre define methods

2) User define methods

Pre Define Method

Predefined methods are provided by the Java language and its libraries. They serve common purposes and are readily available for use in your Java programs. 

Here are some examples of predefined methods and how to use them:

println()

The println() method is part of the System.out class and is used to print text to the console with a newline character. 

Here's an example:

public class PredefinedMethodsExample { public static void main(String[] args) { System.out.println("Hello, world!"); } }

Output:

Hello, world!

Math.sqrt()

The Math.sqrt() method is part of the Math class and is used to calculate the square root of a number. 

Here's an example:

public class PredefinedMethodsExample { public static void main(String[] args) { double number = 16.0; double squareRoot = Math.sqrt(number); System.out.println("The square root of " + number + " is " + squareRoot); } }

Output:

The square root of 16.0 is 4.0

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User Define Method

User-defined methods are created by the programmer to perform specific tasks as needed. You can define your own methods to encapsulate functionality and make your code more organized and reusable. 

Here's an example of a user-defined method:

public class UserDefinedMethodsExample { // User-defined method to add two numbers public static int add(int num1, int num2) { return num1 + num2; } public static void main(String[] args) { int num1 = 5; int num2 = 7; int sum = add(num1, num2); System.out.println("The sum of " + num1 + " and " + num2 + " is " + sum); } }

Output:

The sum of 5 and 7 is 12

In this example, we define a method named add that takes two integers as parameters and returns their sum. The method is then called within the main method.

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Key Differences

Now, let's highlight the key differences between predefined and user-defined methods:

Source: Predefined methods are provided by Java and its libraries, while user-defined methods are created by the programmer.

Availability: Predefined methods are available for use without the need for explicit definition, while user-defined methods must be defined by the programmer.

Purpose: Predefined methods serve common purposes and are used for general tasks. User-defined methods are tailored to specific requirements and are used for custom functionality.

Examples: Predefined methods include println() and Math.sqrt(), while user-defined methods include custom functions created by the programmer.

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Method Parameters and Return Values in Java

In Java, methods are like little workers that do tasks for us. They can use some information (parameters) and give back results (return values). 

Let's dive into this with some really easy examples.

Method Parameters: Giving Information

Imagine you have a friend who can add numbers. You can tell them the numbers you want to add, and they'll do it for you.

public class MethodParametersExample { public static void addNumbers(int num1, int num2) { int sum = num1 + num2; System.out.println("The sum of " + num1 + " and " + num2 + " is " + sum); } public static void main(String[] args) { int number1 = 5; int number2 = 7; addNumbers(number1, number2); // You're telling your friend to add these numbers } }

Output:

The sum of 5 and 7 is 12

Here, you're giving two numbers (5 and 7) as "parameters" to your friend's method, and they use those numbers to do the adding for you.

Return Values: Getting Results

Now, let's say your friend can add numbers and give you back the result.

public class MethodReturnValuesExample { public static int addNumbers(int num1, num2) { return num1 + num2; // Your friend gives you the result } public static void main(String[] args) { int number1 = 5; int number2 = 7; int sum = addNumbers(number1, number2); // You get the result from your friend System.out.println("The sum of " + number1 + " and " + number2 + " is " + sum); } }

Output:

The sum of 5 and 7 is 12

In this case, your friend's method gives you back the result of the addition, which is 12. You can then use that result however you like.

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In short

Method Parameters are like telling your friend what they should work with (in our example, the numbers you want to add).

Return Values are like your friend giving you something in return (in our example, the sum of the numbers).

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Method Overloading

In Java, method overloading is like having a superpower that lets you use the same method name to do different things based on what you need. It's super handy! Let's learn about it in simple terms.

What's Method Overloading?

Method overloading is when you have multiple methods in a class with the same name but different parameters. Java figures out which method to use based on the number or types of parameters you provide.

Why Is It Useful?

Think of it like a chef who can make various types of pizzas with different toppings. They have one name, "makePizza," but they create different pizzas based on what you ask for.

How Does It Work?

Let's see an example to understand this better:

public class PizzaChef { // Method to make a simple pizza public void makePizza() { System.out.println("Made a simple pizza!"); } // Method to make a pizza with one topping public void makePizza(String topping) { System.out.println("Made a pizza with " + topping + "!"); } // Method to make a pizza with two toppings public void makePizza(String topping1, String topping2) { System.out.println("Made a pizza with " + topping1 + " and " + topping2 + "!"); } public static void main(String[] args) { PizzaChef chef = new PizzaChef(); chef.makePizza(); // Makes a simple pizza chef.makePizza("mushrooms"); // Makes a pizza with mushrooms chef.makePizza("pepperoni", "cheese"); // Makes a pizza with pepperoni and cheese } }

Output:

Made a simple pizza!

Made a pizza with mushrooms!

Made a pizza with pepperoni and cheese!

In this example, our PizzaChef class has three makePizza methods. Each method has a different number of toppings as parameters. When you call the method, Java figures out which one to use based on the toppings you provide.

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In short

Method overloading lets you use the same method name with different parameters.

Java decides which method to use based on the number or types of parameters you provide.

It's like having a superpower to make your code more flexible and easier to use!