fixes #77 (#141)

Author: aananya27

Java Design Patterns/DAO pattern/DaoPatternDemo.java

@@ -0,0 +1,20 @@
+public class DaoPatternDemo {
+   public static void main(String[] args) {
+      StudentDao studentDao = new StudentDaoImpl();
+
+      //print all students
+      for (Student student : studentDao.getAllStudents()) {
+         System.out.println("Student: [RollNo : " + student.getRollNo() + ", Name : " + student.getName() + " ]");
+      }
+
+
+      //update student
+      Student student =studentDao.getAllStudents().get(0);
+      student.setName("Michael");
+      studentDao.updateStudent(student);
+
+      //get the student
+      studentDao.getStudent(0);
+      System.out.println("Student: [RollNo : " + student.getRollNo() + ", Name : " + student.getName() + " ]");		
+   }
+}

Java Design Patterns/DAO pattern/Student.java

@@ -0,0 +1,25 @@
+public class Student {
+   private String name;
+   private int rollNo;
+
+   Student(String name, int rollNo){
+      this.name = name;
+      this.rollNo = rollNo;
+   }
+
+   public String getName() {
+      return name;
+   }
+
+   public void setName(String name) {
+      this.name = name;
+   }
+
+   public int getRollNo() {
+      return rollNo;
+   }
+
+   public void setRollNo(int rollNo) {
+      this.rollNo = rollNo;
+   }
+}

Java Design Patterns/DAO pattern/StudentDao.java

@@ -0,0 +1,8 @@
+import java.util.List;
+
+public interface StudentDao {
+   public List<Student> getAllStudents();
+   public Student getStudent(int rollNo);
+   public void updateStudent(Student student);
+   public void deleteStudent(Student student);
+}

Java Design Patterns/DAO pattern/StudentDaoImpl.java

@@ -0,0 +1,38 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class StudentDaoImpl implements StudentDao {
+	
+   //list is working as a database
+   List<Student> students;
+
+   public StudentDaoImpl(){
+      students = new ArrayList<Student>();
+      Student student1 = new Student("Robert",0);
+      Student student2 = new Student("John",1);
+      students.add(student1);
+      students.add(student2);		
+   }
+   @Override
+   public void deleteStudent(Student student) {
+      students.remove(student.getRollNo());
+      System.out.println("Student: Roll No " + student.getRollNo() + ", deleted from database");
+   }
+
+   //retrive list of students from the database
+   @Override
+   public List<Student> getAllStudents() {
+      return students;
+   }
+
+   @Override
+   public Student getStudent(int rollNo) {
+      return students.get(rollNo);
+   }
+
+   @Override
+   public void updateStudent(Student student) {
+      students.get(student.getRollNo()).setName(student.getName());
+      System.out.println("Student: Roll No " + student.getRollNo() + ", updated in the database");
+   }
+}