Methods in Java

Last Updated: 18 November, 2023

A method is a set of instructions. These instructions are enclosed within a pair of curly braces and designed to perform a specific task. Every method has a name, and it may take some parameters and return some values after execution.

Methods are used to organize and reuse code, making it easier to write and maintain complex programs.

In Java, all the methods must be declared inside a class and are executed only when they are called. A method can be called one or more times based on the requirement. A method can be accessed outside the class based on the access modifier.

📝  A method is also known as a function.

Key Characteristics of Methods:

1. Modularization: Methods are used to break down complex programs into smaller, more manageable units.

2. Reusability: Methods can be called repeatedly throughout the program wherever required; reusability saves time and effort.

3. Readability: Methods enhance code readability by facilitating the grouping of logically related instructions.

4. Data Encapsulation: Methods can hide implementation details and expose only necessary data to other parts of the program.

Java Method Declaration

In the method declaration, we provide complete information about the method attributes, such as the method name, return type, access modifier, etc.

A Java method has a total of six components, as described below. It is also known as the method header. Let's discuss them one-by-one:

1. Modifier: It defines the access type or access modifier of the method. We can define four types of access modifiers with the method: public, private, protected, and default.

• Public: The public access modifier allows unrestricted access to variables, methods, constructors, or nested classes from anywhere within the program.

• Private: It provides strong access restriction over the method; if a method is declared with a private modifier, then that method is accessible only in the classes in which it is defined.

• Protected: With the protected modifier, the method is accessible within the same package or subclasses in a different package.

• Default: If we don't define any modifier, then that method has a default modifier, and that method is accessible only in the same package.

2. Return Type: After execution, a method may return a value; the value may be a single or multiple of any type, such as primitive or object. If a method does not return any value, then the return type should be void.

3. Method Name: A method name specifies a unique name to identify it. The method name should correspond to the functionality that the method is performing. A method name should start with a lower-case letter in Java.

4. Parameters: The data it may receive and the data values should be a comma-separated list enclosed in a pair of parentheses. If a method does not have a parameter, then use empty parentheses (). If we call a parameterized method, then we must pass the valid parameter values at the time of method calls.

5. Exceptions: According to the method functionality, we write the expected exception name that the method may throw.

6. Method body: It contains a set of instructions that we want to perform through this method; these instructions are enclosed within the pair of curly braces. All these instructions are executed one by one when we call the method.

A pictorial representation of Method Declaration in Java.

Types of Methods in Java

In Java, there are two types of methods:

✅  Predefined Method: These are built-in methods in Java defined in the Java class libraries. We can use these methods according to the requirements. It is also known as the standard library method or built-in method.

✅  User-defined Methods: A method written by a user to perform some specific task is known as a user-defined method.

Creating a method in Java

A method is created inside a class; every method has a name and is responsible for performing some specific task.

Syntax for creating methods in Java

class ClassName { <accessSpecifier> <returnType> methodName (parameters) <exception> { // method body } }

Method calling in Java

A method can be called inside the class or outside the class, depending on the requirement. Let's see how to call a method in Java.

Calling a method outside the class:

1. Instance methods: Using class instance + dot operator + method name

2. Static methods: Using class name + dot operator + method name

Calling a method inside the class:

In the case of calling a method inside the same class, we can directly call that method; we don't need an instance or class name. All the private methods are called inside the class only.

While calling a parameterized method, we need to pass the proper parameters, and if the method has a return type, we should provide the proper receiver.

Example: Method calling in Java

class Test { // Static method static void staticMethod() { System.out.println("It is a Static method"); } // Instance method void instanceMethod() { System.out.println("It is an Instance method"); // Calling private method directly privateMethod(); } // private method only called in the same class. private void privateMethod() { System.out.println("It is a private method"); } // Parameterized method void addition(int a, int b, int c) { System.out.println("Total sum: " + (a + b + c)); } } public class MethodCalling { public static void main(String[] args) { // Calling static method with the help of class name Test.staticMethod(); Test obj = new Test(); // Calling Instance method with the help of class object obj.instanceMethod(); // Calling parameterized method with proper values obj.addition(10, 20, 30); } }

Output

It is a Static method
It is an Instance method
It is a private method
Total sum: 60