What is a Constructor and Its Types?

7 min read
27 September 2023

A constructor is an inevitable part of the object-creating process. If you are an expert programmer, you will be well aware of the features and functions of a constructor. 

However, if you are a newbie in the programming world, you might lack the clear concept of constructors.

Hence, we have curated this blog post with all the necessary information on Java constructors. Learning about the Java constructors and their different types is necessary if you are learning Java programming language. 

Learn Java constructors' nits and grits from this blog post and expand your knowledge barriers. 

What is a Constructor in Java?

A constructor is a similar code block that resembles the method in Java. Developers call constructors in Java when they create instances of the classes. 

A developer will allocate the memory for that object in the specific memory while they call the constructor. 

This particular type of method is applied to initialize the object. Every time a developer creates an object by utilizing a new () keyword, they must call at least one constructor. 

Features of a Constructor in Java

Certainly, like any other software component, constructors come with a set of unique features. The constructors in Java possess the following features:

  1. The constructor's name is similar to that of the name of the class. This is because the Java compiler uses this character to distinguish constructors from the other member functions of that class.
  2. A constructor should not have any sort of return type. Even a void is not allowed. A constructor calls automatically and is used to initiate values. 
  3. One does not have to call a constructor, as it gets called automatically during the object creation. This feature is much different from that of a constructor in C++. In Java, constructor definition is not allowed outside that class. 
  4. In Java, constructors usually initiate every data member or variable of the class. 
  5. Lastly, Java constructors have the feature to get called in multiple numbers inside one class with distinguished parameters. This feature is known as 'constructor overloading.' 

With the definition and features, you may ask the reason for constructors in Java. Let's move on to that part.

Why do We Need a Constructor in Java?

Let's get this part in simple language. You can assume a box. If you think about a box class, you will naturally consider its variables.

A box class has the variables of length, breadth, and height. Now, if you try to create the object of this box class, the box will be allocated to the computer's memory. 

Is it possible to allocate that box with absolutely zero value for its dimensions? The answer is simple: no. 

Hence, developers have to use constructors to store the values of the class variables while the object is being created. 

A developer may carry out the process themselves, or it can be conducted automatically by a default Java constructor. 

Now that you are clear about Java constructors' importance, let's move on to the crucial part of the blog post: the types of Java constructors. 

Types of Constructors in Java

There are four types of constructors in Java. Check out all those four types of Java constructors at the following points:

  • Default Java Constructor

A default Java constructor is created automatically when a programmer creates an object. Now, this is not the usual case. The default constructor is created when the programmer does not declare any constructor explicitly for the class. 

Hence, this particular type of Java constructor cannot be seen in the program. It comes into existence in the class without any definition or special declaration. 

  • No-Argument Java Constructor

Unlike the default Java constructor, a programmer can visualize a no-argument constructor in the class. As the name suggests, a no-argument Java constructor comes with a definite constructor definition but does not accompany any parameter or argument in the class. 

A no-argument Java constructor gets its call when a programmer develops an object for the class. This particular type of Java constructor usually has declared variables crucial for other member functions. 

  • Parameterized Java Constructor

Like the no-argument Java constructor is different from the default Java constructor, similarly, the parameterized Java constructor has a significant factor different from the no-argument Java constructor. 

Unlike a no-argument Java constructor, a parameterized Java constructor comes with an argument or parameter along with the definition and the declaration. 

Moreover, a programmer can pass multiple arguments through a parameterized Java constructor.

However, these constructors are not used in every object creation. They are specialized constructors that overload constructors to distinguish between different constructors with multiple datatypes. 

  • Copy Java Constructor

This is the most noted and distinguished type of constructor in Java. This type of constructor produces objects with the help of other objects within the same class. 

As a result of this action, a copy constructor provides a copy of the previously created object. 

These are different types of constructors in Java. However, while going through the types, you might get confused about the differences between a constructor and a method. Here's a quick review of that. 

How is a Constructor Different from a Method?

If you are a newbie, it is natural to get confused between constructors and methods in the Java programming language. Check out the following points and refresh your Java concept. 

  • constructor in Java initiates the state of the object. At the same time, a method exposes the behavior of that object.
  • A constructor has no return type, but a method has to have a return type.
  • A programmer invokes a constructor implicitly, whereas they invoke a method explicitly.
  • The ide Java compiler will provide a default Java constructor if a programmer has no Java constructor in the class. However, the compiler in Java cannot provide a method to the class, irrespective of any case. 
  • The constructor's name must be similar to the name of the class. But in this method, there is no such compulsory criterion. 

Hope these points help you understand the different features and functions of a method and a constructor in the Java programming language. 

Conclusion

This is a detailed description of a constructor in Java and its different types. The blog post also focused on the importance of constructors in object creation and marked their differences from methods. 

Use this blog post as your ultimate Java constructor guide and polish your Java skills. 

In case you have found a mistake in the text, please send a message to the author by selecting the mistake and pressing Ctrl-Enter.
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