![Default constructor
class. It will be invoked at the
A constructor that have no parameter is known as defaultconstructor.
Syntax of default constructor:
<class_name>(){}
Example of default constructor
In this example, we are creating the no-arg constructor in theBike
time of object creation.
class Bike1{
Bike1(){
System.out.println("Bike is created")
;}
public static void main(Stringargs[]){
Bike1 b=new Bike1();
}
}
5](https://image.slidesharecdn.com/constructor-oopj-210622082211/85/Constructor-oopj-5-320.jpg)
![ Example of parameterized constructor
In this example, we have created the constructor of Student class that have two parameters.
We can have any number of parameters in the constructor.
class Student4{
int id;
String name;
Student4(int i,String n){
id = i;
name = n;
}
void display(){System.out.println(id+" "+name);}
public static void main(String args[]){
Student4 s1 = new Student4(111,"Karan");
Student4 s2 = new Student4(222,"Aryan");
s1.display();
s2.display();
}
}
7](https://image.slidesharecdn.com/constructor-oopj-210622082211/85/Constructor-oopj-7-320.jpg)
![example: constructor overloading example:
classLanguage{
String name;
Language() {
System.out.println("Constructor methodcalled.");
}
Language(String t) {
name = t;
}
public static void main(String[] args) {
Language cpp = new Language();
Language java = new Language("Java");
cpp.setName("C++");
java.getName();
cpp.getName();
}
void setName(String t) {
name = t;
}
void getName() {
System.out.println("Language name: " + name);
}
}
10](https://image.slidesharecdn.com/constructor-oopj-210622082211/85/Constructor-oopj-10-320.jpg)
Constructor oopj
- 2. Constructor Constructor in java is a special type of method that is used to initialize the object. Java constructor is invoked at the time of object creation. It constructsthe values i.e. provides data for the object that is why it is known as constructor. 2
- 3. Rules for creating java constructor There are basically two rules defined for the constructor. 1. Constructor name must be same as its classname 2. Constructor must have no explicit returntype 3
- 4. Types of java constructors There are two types of constructors: 1. Default constructor (no-arg constructor) 2. Parameterizedconstructor 4
- 5. Default constructor class. It will be invoked at the A constructor that have no parameter is known as defaultconstructor. Syntax of default constructor: <class_name>(){} Example of default constructor In this example, we are creating the no-arg constructor in theBike time of object creation. class Bike1{ Bike1(){ System.out.println("Bike is created") ;} public static void main(Stringargs[]){ Bike1 b=new Bike1(); } } 5
- 6. Parameterized constructor A constructor that have parameters is known as parameterizedconstructor. Why use parameterized constructor? Parameterized constructor is used to provide different values to the distinct objects. 6
- 7. Example of parameterized constructor In this example, we have created the constructor of Student class that have two parameters. We can have any number of parameters in the constructor. class Student4{ int id; String name; Student4(int i,String n){ id = i; name = n; } void display(){System.out.println(id+" "+name);} public static void main(String args[]){ Student4 s1 = new Student4(111,"Karan"); Student4 s2 = new Student4(222,"Aryan"); s1.display(); s2.display(); } } 7
- 9. Constructor overloading Like other methods in java constructor can be overloaded i.e. we can create asmany constructors in our class asdesired. Number of constructors depends on the information about attributes of an objectwe have while creating objects. 9
- 10. example: constructor overloading example: classLanguage{ String name; Language() { System.out.println("Constructor methodcalled."); } Language(String t) { name = t; } public static void main(String[] args) { Language cpp = new Language(); Language java = new Language("Java"); cpp.setName("C++"); java.getName(); cpp.getName(); } void setName(String t) { name = t; } void getName() { System.out.println("Language name: " + name); } } 10
- 11. Output: Constructor method called. Language name: java Language name:c++ 11
- 12. 12