Visitor Design Pattern - University Lecture Application

Special subjects are taught by Visiting Faculty

Author: premaseem

pattern/src/com/premaseem/ClientStudent.java

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+package com.premaseem;
+
+import java.util.Scanner;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+public class ClientStudent {
+    public static void main (String[] args) {
+        System.out.println();
+        System.out.println("University Lecture application designed using Visitor design pattern \n");
+        System.out.println("Subject available for lectures are:-");
+        System.out.println("Maths");
+        System.out.println("Computers");
+        System.out.println("Aviation");
+        System.out.println();
+        System.out.println("Please pick subject ...");
+
+        Scanner scanner = new Scanner(System.in);
+        String subjectOption = scanner.next();
+        if (subjectOption.equalsIgnoreCase("Maths")){
+            System.out.println("Math can be taught by in house Faculty");
+            Subject subject = new Maths();
+            subject.teach();
+        }
+
+        if (subjectOption.equalsIgnoreCase("Computers")){
+            System.out.println("Computers needs visiting Faculty, lets call Prof. Prem Aseem Jain :-)");
+            Subject subject = new Computer();
+            VisitingFaculty profAseem = new ProfAseem();
+            subject.acceptVisitingFacultytoTeach(profAseem);
+        }
+
+        if (subjectOption.equalsIgnoreCase("Aviation")){
+            System.out.println("Aviation needs visiting Faculty, lets call Prof. Prem Aseem Jain :-)");
+            Subject subject = new Aviation();
+            VisitingFaculty profAseem = new ProfAseem();
+            subject.acceptVisitingFacultytoTeach(profAseem);
+        }
+
+        System.out.println("Class over - Go Home and have fun :-) ");
+
+    }
+}

pattern/src/com/premaseem/Subject.java

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+package com.premaseem;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+public abstract class Subject {
+
+    abstract void acceptVisitingFacultytoTeach (VisitingFaculty visitingFaculty);
+
+    void teach(){
+           System.out.println("IN-HOUSE Faculty teaching "+ this.getClass().getSimpleName()+" subject");
+       }
+}
+
+class Aviation extends Subject{
+
+    @Override
+    void acceptVisitingFacultytoTeach (VisitingFaculty visitingFaculty) {
+        visitingFaculty.teach(this);
+    }
+}
+
+class Computer extends Subject{
+
+    @Override
+    void acceptVisitingFacultytoTeach (VisitingFaculty visitingFaculty) {
+        visitingFaculty.teach(this);
+    }
+}
+
+class Maths extends Subject{
+
+    @Override
+    void acceptVisitingFacultytoTeach (VisitingFaculty visitingFaculty) {
+        visitingFaculty.teach(this);
+    }
+}

pattern/src/com/premaseem/VisitingFaculty.java

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+package com.premaseem;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+public interface VisitingFaculty {
+    void teach (Aviation aviation);
+    void teach (Computer computer);
+    void teach (Maths maths);
+}
+
+class ProfAseem implements VisitingFaculty{
+
+    @Override
+    public void teach (Aviation aviation) {
+        System.out.println("Visiting Faculty teaching Aviation subject");
+    }
+
+    @Override
+    public void teach (Computer computer) {
+        System.out.println("Visiting Faculty teaching Computer subject");
+    }
+
+    @Override
+    public void teach (Maths maths) {
+        System.out.println("Visiting Faculty teaching Maths subject");
+    }
+}
+
+class AnyOtherProfessor implements VisitingFaculty{
+
+    @Override
+    public void teach (Aviation aviation) {
+        System.out.println("Visiting Faculty teaching Aviation subject");
+    }
+
+    @Override
+    public void teach (Computer computer) {
+        System.out.println("Visiting Faculty teaching Computer subject");
+    }
+
+    @Override
+    public void teach (Maths maths) {
+        System.out.println("Visiting Faculty teaching Maths subject");
+    }
+}