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| Structural Design Patterns |
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//
questions.questDB = new CsharpQuestions();
//
questions.questDB = new CplusplusQuestions();
questions.display();
questions.next();
questions.newOne(“What is polymorphism? ”);
questions.newOne(“How many types of
polymorphism are there in java?”);
questions.displayAll();
}}
Here is the output of the above program:
C:\ Command Prompt
C:\> javac TestBridge.java
C:\> java TestBridge
What is Java?
~~~~~~~~~~~~~~~~~~~~~~~~
Question Catalog: Java Language
What is Java?
What is marker interface?
What is cross-platform?
How multiple polymorphism is achieved in
java?
How many types of exception handling are
there in java?
Define the keyword final for variable, method,
and class in java?
What is multi-tasking?
What is multi-threading?
What is polymorphism?
How many types of polymorphism are there in
java?
~~~~~~~~~~~~~~~~~~~~~~~~
The above example tries to show how the
Bridge pattern decouples the interface from
its implementation. One can easily notice that
the class JavaQuestion can be launched
independently working as an independent system.
III. Composite Pattern:
Individual objects as well as the composite
objects can be represented with the Composite
Design Pattern. Composite pattern represents |
|
these objects with a tree structure. Suppose,
within a company, there is an employee
hierarchy where a manager has its
subordinates, Project Leader also has the
subordinates, while the developer has no subordinates.
Benefits: It is more flexible as compared to
the static inheritance. It simplifies coding by
implementing each feature in a class. It
enhances the capability of an object as the new
classes are created to add new features and make some changes.
Usage: This design pattern is used when the responsibilities are needed to be added
dynamically to the individual objects without
affecting other objects. Where an object’s
responsibilities may vary from time to time. Now, let’s try to solve the above problem
technically.
Develop a class “Employee” having the
getters and setters for the attributes
empname, empsal and emp subordinates.
Employee.java
class Employee {
String Empname;
double Empsalary;
Employee(String n, double s){
Empname = n;
Empsalary = s;
}
String getName() {
return Empname;
}
double getSalary() {
return Empsalary;
}
public String toString() {
return ”Employee” + Empname;
}
}
For example, General Manager may have
several employee and some of them are
Managers, further these managers have
several employees. To illustrate all these things, let’s design a simple Manager class. |
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Oct 2007 | Java Jazz Up | 53 |
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