Constructor in JAVA


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.

For example:

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.

For example,

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);
Python Programming ↓ 👆
Java Programming ↓ 👆
JAVA covered following topics in these notes.
JAVA Programs
Principles of Programming Languages ↓ 👆
Principles of Programming Languages covered following topics in these notes.

Previous years solved papers:
A list of Video lectures References:
  1. Sebesta,”Concept of programming Language”, Pearson Edu 
  2. Louden, “Programming Languages: Principles & Practices” , Cengage Learning 
  3. Tucker, “Programming Languages: Principles and paradigms “, Tata McGraw –Hill. 
  4. E Horowitz, "Programming Languages", 2nd Edition, Addison Wesley

    Computer Organization and Architecture ↓ 👆

    Computer Organization and Architecture covered following topics in these notes.

    1. Structure of desktop computers
    2. Logic gates
    3. Register organization
    4. Bus structure
    5. Addressing modes
    6. Register transfer language
    7. Direct mapping numericals
    8. Register in Assembly Language Programming
    9. Arrays in Assembly Language Programming


    1. William stalling ,“Computer Architecture and Organization” PHI
    2. Morris Mano , “Computer System Organization ”PHI

    Computer Network ↓ 👆
    Computer Network covered following topics in these notes.
    1. Data Link Layer
    2. Framing
    3. Byte count framing method
    4. Flag bytes with byte stuffing framing method
    5. Flag bits with bit stuffing framing method
    6. Physical layer coding violations framing method
    7. Error control in data link layer
    8. Stop and Wait scheme
    9. Sliding Window Protocol
    10. One bit sliding window protocol
    11. A protocol Using Go-Back-N
    12. Selective repeat protocol
    13. Application layer
    1. Andrew S. Tanenbaum, David J. Wetherall, “Computer Networks” Pearson Education.
    2. Douglas E Comer, “Internetworking with TCP/IP Principles, Protocols, And Architecture",Pearson Education
    3. KavehPahlavan, Prashant Krishnamurthy, “Networking Fundamentals”, Wiley Publication.
    4. Ying-Dar Lin, Ren-Hung Hwang, Fred Baker, “Computer Networks: An Open Source Approach”, McGraw Hill.