Difference Between Constructor and Method
Have you ever wondered about the difference between a constructor and a method? A constructor initializes a new object, has no return type, and shares its name with the class. In contrast, a method defines behaviours, can return values, and has a unique name. Let's understand more!
A constructor is a special type of method in a class that is automatically called when an instance of that class is created. While, A method in OOP is a block of code within a class that performs a specific task. In this blog, we will see the differences between them in detail!
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Difference Between Constructor and Method
Below is a table showing the differences between Constructors and Methods.
| Aspect |
Constructor |
Method |
| Purpose |
Used to initialize the state of an object. |
Used to exhibit the behaviour of an object. |
| Name |
It must have the same name as the class. |
Can have any name different from the class. |
| Return Type |
Does not have a return type, not even void. |
Must have a return type, can be void. |
| Calling |
Automatically called when an object is created. |
It must be called explicitly. |
| It cannot be inherited. |
It can be inherited. |
|
| It can be overloaded. |
It can be overloaded and overridden. |
|
| Invoking |
It cannot be invoked explicitly, invoked by new. |
It can be invoked by object reference. |
| Default Version |
A default constructor is provided if none is specified. |
No default method is provided. |
What is a Constructor?
A constructor is a special type of method in object-oriented programming used to initialize a newly created object. It prepares the new object for use, often by assigning initial values to its member variables.
Key Characteristics and Functions of a Constructor
- Name: The constructor has the same name as the class in which it is declared.
- No Return Type: Unlike other methods, constructors do not have a return type, not even void.
- Automatic Invocation: A constructor is called automatically when a new instance of an object is created with the new keyword.
- Initialization: Constructors set up the initial state of an object. This might include setting default values or performing any setup steps required for the object to be used properly.
- Overloading: Constructors can be overloaded, meaning a class can have more than one constructor, each with a different number or type of parameters.
- Inheritance: Constructors are not inherited by subclasses. However, a subclass constructor can call a constructor of its superclass, typically using super() in languages like Java and C#.
- Default Constructor: If no constructor is explicitly defined in a class, many programming languages provide a default constructor that initializes the object with default values.
public class Vehicle { private String type;
// Constructor public Vehicle(String type) { this.type = type; }}
In this example, Vehicle(String type) is a constructor that initializes the Vehicle object with a specific type.
What is a Method?
A method in object-oriented programming (OOP) is a procedure or function associated with a class. Methods are essentially blocks of code that are designed to perform a specific task and are a fundamental part of classes in OOP. They define the behaviours or actions that an object of a class is able to perform.
Key Characteristics and Functionalities of a Method
- Encapsulation: Methods are encapsulated within a class and operate on the data contained within the class (though they can also use external data passed to them).
- Syntax: A method typically has a name, a return type (which can be a data type like int, string, or a class, or void if it returns nothing), a list of parameters (optional), and a body that defines what the method does.
- Calling/Invocation: Methods are called or invoked on objects or classes. When a method is called on an object, it may alter the state of the object or perform a computation and return a result.
- Access Modifiers: Methods can have access modifiers (like public, private, protected in many languages) that define their visibility and where they can be accessed from.
- Overloading and Overriding: Methods can be overloaded (same method name with different parameters) and overridden (a subclass provides a specific implementation for a method that is already defined in its superclass).
- Return Value: After executing, a method can return a value. The void keyword is used when a method does not return any value.
- Parameters: Methods can take parameters, which are variables used to pass data into the method.
For example, in Java
public class Vehicle { private String type;
public Vehicle(String type) { this.type = type; }
// Method public void displayType() { System.out.println("The type of vehicle is " + type); }}
In this example, displayType() is a method that performs the action of displaying the type of the vehicle. It is called on an instance of the Vehicle class.
Read Later
Thus, while both constructors and methods are fundamental elements in object-oriented programming and share some similarities, such as being members of a class and having the ability to take parameters, they serve distinct purposes and have different characteristics.
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FAQs
What is the primary purpose of a constructor compared to a method in Java?
A constructor is a special type of method in Java used to initialize objects of a class, typically setting initial values for member variables. In contrast, a method is a general-purpose function that performs a specific task or operation when invoked.
How do constructors and methods differ in terms of return type and name?
Constructors have no return type, not even void, and their name must match the name of the class. Methods, however, can have any return type, including void, and their names are arbitrary, as long as they follow Java's naming conventions.
When are constructors called compared to methods?
Constructors are automatically called when an object of a class is created using the new keyword or when object instantiation occurs. Methods, on the other hand, are explicitly called by name to perform a specific operation on an object or class.
Can constructors be overloaded and what about methods?
Yes, constructors can be overloaded, meaning a class can have multiple constructors with different parameters. Similarly, methods can also be overloaded, allowing a class to have multiple methods with the same name but different parameter lists.
What is the role of access modifiers in constructors and methods?
Constructors and methods can have access modifiers like public, private, or protected to control their visibility and accessibility. However, constructors are typically used to initialize the state of an object, so they are often public or protected, whereas methods can have varying access levels based on their purpose and usage.
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