Download Library System Version: 1.0 Program to implement constructors Date

Library System
Program to implement constructors
Version: 1.0
Date:
Library system
Defining classes using constructor
Version 1.0
Revision History
Date
Version
1.0
Description
Author
Original Program
Title: Using constructors
Estimated time to complete this experiment: 2 hrs
Objective: Defining classes using constructor with display function
Confidential
St. Francis Institute of Technology
(Engg. College)
Page 2
Library System
Program to implement constructors
Version: 1.0
Date:
Books/ Journals/ Websites referred:
http://javarevisited.blogspot.in/2012/12/what-is-constructor-in-java-example-chainning-overloading.html
http://en.wikipedia.org/wiki/Constructor_(object-oriented_programming)
http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
Pre Lab/ Prior Concepts:
Constructor in Java is block of code which is executed at the time of Object creation. But other than
getting called, Constructor is entirely different than methods and has some specific properties like name
of constructor must be same as name of Class. Constructor also can not have any return type,
constructor’s are automatically chained by using this keyword and super. Since Constructor is used to
create object, object initialization code is normally hosted in Constructor. Similar to method you can
also overload constructor in Java.
New Concepts to be learned:
A class contains constructors that are invoked to create objects from the class blueprint. Constructor
declarations look like method declarations—except that they use the name of the class and have no
return type. For example, Bicycle has one constructor:
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
To create a new Bicycle object called myBike, a constructor is called by the new operator:
Bicycle myBike = new Bicycle(30, 0, 8);
new Bicycle(30, 0, 8) creates space in memory for the object and initializes its fields.
Although Bicycle only has one constructor, it could have others, including a no-argument constructor:
public Bicycle() {
gear = 1;
cadence = 10;
speed = 0;
}
Bicycle yourBike = new Bicycle(); invokes the no-argument constructor to create a new Bicycle object
called yourBike.
Both constructors could have been declared in Bicycle because they have different argument lists. As
with methods, the Java platform differentiates constructors on the basis of the number of arguments in
the list and their types. You cannot write two constructors that have the same number and type of
arguments for the same class, because the platform would not be able to tell them apart. Doing so
causes a compile-time error.
Confidential
St. Francis Institute of Technology
(Engg. College)
Page 2
Library System
Program to implement constructors
Version: 1.0
Date:
Requirements:
Software & Hardware Required:
Text editor, jdk1.6.0_16, Command Prompt
Conclusion:
Hence the above program shows the implementation of constructors in Java
Real Life Application:
In object-oriented programming, a constructor (sometimes shortened to ctor) in a class is a special type
of subroutine called to create an object. It prepares the new object for use, often accepting parameters
that the constructor uses to set member variables required
Post Lab Questions:
What is constructor chaining?
Constructor chaining occurs through the use of inheritance. A subclass constructor method's first
task is to call its superclass' constructor method. This ensures that the creation of the subclass
object starts with the initialization of the classes above it in the inheritance chain.
There could be any number of classes in an inheritance chain. Every constructor method will call
up the chain until the class at the top has been reached and initialized. Then each subsequent
class below is initialized as the chain winds back down to the original subclass.
Viva Questions: Explain the behavior of constructors under inheritance.
Confidential
St. Francis Institute of Technology
(Engg. College)
Page 2