Constructors


Thursday, November 9, 2023

In object-oriented programming (OOP) in Java, constructors play a crucial role by providing a way to initialize objects of a class. A constructor is a special method that is automatically called when an object is created from a class. Its main function is to assign initial values to the attributes of the class and perform any necessary initialization.

Definition and Function of Constructors

In Java, a constructor has the same name as the class and has no return type. It is automatically executed when the new keyword is used to create a new object. Constructors are essential to ensure that objects are created in a valid and consistent state.

public class Person {
    // Attributes
    String name;
    int age;

    // Constructor without parameters
    public Person() {
        name = "Unnamed";
        age = 0;
    }

    // Constructor with parameters
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

Usage of the this Keyword

The this keyword is used within a constructor to refer to the current instance of the class. In the second constructor of the example, this.name and this.age are used to distinguish between the constructor parameters and the class attributes.

Constructors and Overloading

Java allows constructor overloading, which means that a class can have multiple constructors with different parameter lists. This provides flexibility when creating objects, as different constructors can be used based on the programmer's needs.

Benefits of Using Constructors

  • Consistent Initialization: Constructors ensure that objects are created in a consistent initial state.
  • Flexibility in Object Creation: Constructor overloading allows creating objects with different configurations based on program requirements.
  • Avoids Invalid States: Constructors help avoid objects being in invalid states by providing appropriate initial values.
  • Improves Code Clarity: The use of clear and well-defined constructors enhances code readability and understanding.

Share it

Share it on your social media and challenge your friends to solve programming problems. Together, we can learn and grow.

Copied

The code has been successfully copied to the clipboard.

More Exercises

Continue improving your Java programming skills with our selection of practical exercises from the lesson. Click on Practice and challenge your knowledge!

1

Classes and objects

Delve into the basics of object-oriented programming in Java. Learn about classes and objects, the essential components that breathe life into modularity and code reusability in this versatile programming language.

2

Attributes and Methods

Dive into the essence of object-oriented programming in Java by gaining a deep understanding of attributes and methods. Explore how these fundamental elements are crucial for creating classes and objects, providing modularity and efficiency in software development.

3

Constructors

Discover the importance of constructors in Java and how they crucially initialize objects. Learn best practices to ensure consistency in instance creation and optimize your code with our detailed examples.

4

Access Modifiers

5

Getters and Setters Methods

Learn how to create secure interfaces with getters and setters methods in Java. Explore how these methods promote encapsulation and provide precise control over attribute modification.

6

Person class and method ToString()

Create a Java program that requests three names of people from the user and stores them in an array of objects of type Person.

7

Constructors and destructors

Create a Java program that prompts the user for three names of people and stores them in an array of Person-type objects.

8

instanceof operator

The instanceof operator in Java is used to check if an object is an instance of a specific class, subclass, or implements a specific interface.

9

Class person, student and teacher

Create a new Java project with three classes plus another class to test the logic of the code. The main classes of the program are the following.

10

Nested and inner classes

Nested and Inner Classes in Java are defined within another class and have access to the members of the containing class, including private members.

11

Inheritance

Inheritance in Java is one of the fundamental pillars of Object-Oriented Programming (OOP). It provides a mechanism through which a class can inherit properties and behaviors from another class.

12

Photo book class

Create a Java program to manage a photo book using object-oriented programming.

13

Creating Classes and Objects

Create a class called 'Person' with attributes like name, age, and address. Then, create objects of the 'Person' class and initialize their attributes. Implement methods to display and modify these attributes.

14

Inheritance of objects

Create a Java program that prompts the user for three names of people and stores them in an array of Person-type objects.

15

Abstract classes

An abstract class is a class that cannot be instantiated directly. This means you cannot create objects directly from an abstract class using the new operator.

16

Shapes - Class diagram

Create a Java program that represents the following UML class diagram.

17

Interfaces

Create a Java program that implements an IVehiculo interface with two methods, one for Drive of type void and another for Refuel of type bool that has a parameter of type integer with the amount of gasoline to refuel.

18

Abstract classes

Create a Java program that implements an abstract class Animal that has a Name property of type text and three methods SetName (string name), GetName and Eat.

Object-oriented programming

Practice object-oriented programming exercises in Java. Learn to use constructors, destructors, inheritance, interfaces among others.

Fundamentals concepts
Practice exercises

Keep learning

C# Programming Course

Free programming course with practical exercises and solutions in C#. Start learning right now!

Exercises C# App

Take your Exercises C# lessons everywhere with our Android app. Download it now from Google Play