A constructor is a method which called when an instance of an object is created.
If programmer do not provide a constructor for a class, Java will automatically create a default constructor with no parameters and doesn’t initialise any fields.
Default constructor is called if we specify the new keyword without passing parameters.
Professor p =new Professor();// constructor is called
Here a variable (p) type Professor is created, using default constructor of class Professor.
If we declare any constructor for a class, than Java does not create a default constructor for that class.
If we created a constructor which accept parameter or constructor which do not accept parameter, than Java will not declare any default constructor.
Some points to know about constructors are:
- It does not have a return type.
- Constructors are not considered as member of the class.
- The name of the constructor must be same as the name of the class.
- Keyword public before constructor name shows it can be accessible by other classes too.
- A constructor supports exception handling.
- A constructor can be created for each class.
- A constructor can be overloaded, if having unique signature.
- For example,
- Professor p = new Professor(“Jayesh” , “Burhanpur”);
- Professor p = new Professor(“Jayesh” , “Burhanpur” , 9xxxxx9);