Constructor can be defined as a block similar to a method, having same name as that of class name..
Example Code for Constructor:
public class Student {
public Student{
}
public static void main(String[] args){
// so here what we have to do is just create an object like
Student st = new Student(); // and that’s all, here we don’t need to write any reference like
st.Student();
}
}Watch the Video On Constructors in Java, For Live programming:
Use of Constructor in Java:
- Constructor can be defined as a block similar to a method, having same name as that of class name..
- Constructor have doesn’t any return type.
- Modifiers which we can use for constructors are public, protected, default and private only. It can’t be abstract, static, final and synchronized.
- how we run constructor in java? So constructor executes automatically, when we create an object. we don’t need to execute like a method.
Types of Constructor in Java:
- Default Constructor
- Parameterized Constructor
1. Default Constructor: Also we called it as no-arg constructor,arg simply means arguments. A constructor is called as default constructor when it doesn’t have any parameter. The syntax of default constructor is like: <class_name>(){}
Program for Default Constructor:
class Bike{
Bike(){
System.out.println(“Bike is perfect”);
}
public static void main(String[] args){
Bike b = new Bike();
}
}Output: Bike is perfect
The default constructor is used to provide the default values to the object which is 0, null, etc.. which is depending on the type.
class Bike{
int mileage;
String model;
void Bike1(){
System.out.println(mileage+” “+model);
}
public static void main(String[] args){
Bike b = new Bike();
b.Bike1();
}
}Output: 0 null
The compiler here is provides a default constructor. As you can see at the output 0 and null which is provided by default constructor.
1. Parameterized Constructor:
Parameterized Constructors are basically used to provide same and different values to distinct objects.
Program for Parameterized Constructor:
class Student{
int id;
String name;
Student(int i,String n){
id = i;
name = n;
}
void display(){
System.out.println(id+” “+name);
}
public static void main(String args[]){
Student s1 = new Student(101,”Java”);
Student s2 = new Student(202,”Android”);
s1.display();
s2.display();
}
}