A constructor in Java is a special type of method used to initialize objects. It is called when an object of a class is created. Constructors have the same name as the class and do not have a return type.
void.class Dog {
Dog() {
System.out.println("A new dog object is created!");
}
}
public class Main {
public static void main(String[] args) {
Dog myDog = new Dog(); // Calls the default constructor
}
}class Dog {
String name;
int age;
Dog(String name, int age) {
this.name = name;
this.age = age;
}
void display() {
System.out.println("Dog's Name: " + name + ", Age: " + age);
}
}
public class Main {
public static void main(String[] args) {
Dog myDog = new Dog("Buddy", 3); // Calls the parameterized constructor
myDog.display();
}
}Just like methods, constructors can also be overloaded by having multiple constructors with different parameters in a class.
class Dog {
String name;
int age;
// Default constructor
Dog() {
this.name = "Unknown";
this.age = 0;
}
// Parameterized constructor
Dog(String name, int age) {
this.name = name;
this.age = age;
}
void display() {
System.out.println("Dog's Name: " + name + ", Age: " + age);
}
}
public class Main {
public static void main(String[] args) {
Dog dog1 = new Dog(); // Calls the default constructor
Dog dog2 = new Dog("Buddy", 3); // Calls the parameterized constructor
dog1.display();
dog2.display();
}
}Constructor chaining refers to the process of calling one constructor
from another constructor within the same class or from a superclass
constructor. This can be done using the this() or
super() keywords.
this():class Dog {
String name;
int age;
Dog() {
this("Unknown", 0); // Calls the parameterized constructor
}
Dog(String name, int age) {
this.name = name;
this.age = age;
}
void display() {
System.out.println("Dog's Name: " + name + ", Age: " + age);
}
}
public class Main {
public static void main(String[] args) {
Dog dog1 = new Dog(); // Calls the default constructor
Dog dog2 = new Dog("Buddy", 3); // Calls the parameterized constructor
dog1.display();
dog2.display();
}
}super() to Call Superclass Constructorssuper() keyword is used to call the constructor of
the superclass. It must be the first statement in the subclass
constructor.class Animal {
Animal() {
System.out.println("Animal is created");
}
}
class Dog extends Animal {
Dog() {
super(); // Calls the superclass constructor
System.out.println("Dog is created");
}
}
public class Main {
public static void main(String[] args) {
Dog myDog = new Dog();
}
}Constructors are essential in Java for initializing objects and providing flexibility in object creation. Understanding constructors and their various types helps in writing more efficient and maintainable code.
Please subscribe or like our page for newsletters