1. 1 - Aggregation - UML diagram - Self-Referential Classes - Generisity

2. Class Circle public class Circle { private double xCenter; // x center coordinate private double yCenter; // y center coordinate private double radius; // circles radius public Circle(double xCenter, double yCenter, double radius ) { this.xCenter = xCenter; this.yCenter = yCenter; this.radius = radius; } // class Circle constructor // rest methods. } // class Circle 2

3. Class Point public class Point { private double x; // x coordinate private double y; // y coordinate public Point(double x, double y) { this.x = x; this.y =y; } // class Point constructor public double getX( ) { return this.x; } public void printPoint() { System.out.println( "x = “ + this.x + "y = “ + this.y); } // printPoint() // rest methods } // class Point 3

4. Aggregation ( הכלה ) public class Circle { private Point center; // another object ! private double radius; // circles radius public Circle( Point center, double radius ) { this.center = center; this.radius = radius; } // class Point constructor public Point getCenter() { return this.center; } public double getRadius() { return this.radius; } // rest methods Aggregation is a relationship between two classes. The aggregate class contains a reference to another class. These methods use reference center to another object Point.

5. Aggregation – example 1 Circle (c1) centerradius p15.0 c1 Point (p1) xy 7.49.5 p 1 Point p1 = new Point(7.4,9.5); // create new point Circle c1 = new Circle(p1,5.0); // create new circle : reference to object p1 5

6. Access to point coordinates public static void main(String[ ] args) { Point p1 = new Point(7.4,9.5); // create new point Circle c1 = new Circle(p1,5.0); // create new circle Point c1Center = c1.getCenter(); double c1CenterX = c1Center.getX(); double c1CenterY = c1Center.getY(); double c1Radius = c1.getRadius(); System.out.println(“x= “+ c1CenterX+” y= “+c1CenterY + “ r= “+ c1Radius); // another choice c1CenterX = c1.getCenter(). getX(); c1CenterY = c1.getCenter(). getY(); p1.printPoint(); } // main We use getter methods from Point object This program generates the following output: x = 7.4 y = 9.5 r = 5.0 x = 7.4 y = 9.5 We use getter methods from Circle object 6

7. Rectangle definition 7 Rectangle is any quadrilateral with four right angles. The word rectangle comes from the Latin rectangulus, which is a combination of rectus ( right ) and angulus ( angle ). bottomLeft topRight x - axis y - axis bottomLeft x - axis y - axis width height

8. Class Rectangle 8 public class Rectangle { private Point bottomLeft; private Point topRight; public Rectangle (Point bottomLeft, Point topRight) { this.bottomLeft = bottomLeft; this.topRight = topRight; } // constructor1 public Rectangle (Point bottomLeft, double width, double height) { this.bottomLeft = new Point(bottomLeft); this.topRight = new Point(bottomLeft.getX() + width, bottomLeft.getY() + height); } // constructor2 public double getArea() } double width = this.topRight.getX() - this.bottomLeft.getX(); double height = this.topRight.getY() - this.bottomLeft.getY(); return width * height; { // getArea

9. Class Rectangle, cont. 9 public double getPerimeter() { double width = this.topRight.getX() - this.bottomLeft.getX(); double height = this.topRight.getY() - this.bottomLeft.getY(); return (2 * width) + (2 * height); { // getPerimeter public void move (double deltaX, double deltaY) { this.topRight.setX(this.topRight.getX() + deltaX); this.topRight.setY(this.topRight.getY() + deltaY); this.bottomLeft.setX(this.bottomLeft.getX() + deltaX); this.bottomLeft.setY(this.bottomLeft.getY() + deltaY); { // move public String toString() { return "Rectangle:" + "\n" + "bottom-left point : " + this.bottomLeft.toString() + "\n" + "top-right point : " + this.topRight.toString(); { // toString } // class Rectangle

10. Class Rectangle, cont. public static void main(String[] args) { Point p1 = new Point(2,1); Point p2 = new Point(7,5); Rectangle rect1 = new Rectangle(p1,p2); System.out.println(rect1); double width = 6.0; double height = 3.0; Rectangle rect2 = new Rectangle(p1,width,height); System.out.println(rect2); System.out.println("area = " + rect1.getArea()); System.out.println("perimeter = "+ rect2.getPerimeter()); } // main 10 Rectangle: bottom-left point : x = 2.0 y =1.0 top-right point : x = 7.0 y = 5.0 Rectangle: bottom-left point : x = 2.0 y =1.0 top-right point : x = 8.0 y = 4.0 area = 20.0 perimeter = 18.0

11. Encapsulation ( הכמסה ) One of the important object-oriented techniques is hiding the data ( הסתרת מידע (within the class, and making it available only through the methods. This technique is often known as encapsulation, because it seals the class's data (and internal methods) safely inside the "capsule" of the class, where it can be accessed only by trusted users- i.e., by the methods of the class. The most important reason is to hide the internal implementation details of your class. If a variable is visible only in your class, you have to document it. 11

12. Rectangle Point bottonLeft Point topRight Rectangle( Point bottonLeft, Point topRight) Rectangle( Point bottonLeft, double width, double height) double getArea() double getPerimeter() void move(double deltaX, double deltaY) String toString() UML Diagram – Example1 UML stands for Unified Modeling Language. It's a way to represent object-oriented applications using graphical diagrams. UML shows the classes of the system, their relationships, and the operations and attributes of the classes. 12 Point public double x public double y Point(double x, double y) double getX() double getY() void setX(double x) void setY(double y) String toString()

13. UML Diagram – Example2 13 Lecturer String name int depCode Lecturer(String name,int depCode) String getName() void setDepCode( int depCode) Student String name int ID Lecturer lecturer Student(String name, int ID, Lecturer lecturer) String getName() void setID( int ID) Lecturer getLecturer() ● UML diagrams allow us to denote the relationships between classes. ● In a UML diagram we can show the class member variables and class methods.

14. Aggregation – example 2 Lecturer namedepCode Alex777 lect Student nameIDlecturer David1234567lect Student nameIDlecturer Ronit7654321lect s1s2 14 Lecturer lect = new Lecturer(“Alex”, 777); Student s1 = new Student(“David”, 1234567, lect); Student s2 = new Student(“Ronit”, 7654321, lect);

15. Array of objects Student [ ] arr = new Student [ 5 ]; arr[ ] 01234 null arr arr[ ] 01234 arr[0]arr[1]null Lecturer lect = new Lecturer(“Alex”, 777); arr[0] = new Student(“David”,1234567,lect); arr[1] = new Student(“Ronit”,7654321,lect); Student nameIDlecturer David1234567lect Student nameIDlecturer Ronit7654321lect 15

16. Insertion sort - reminder The insertion sort algorithm works by inserting each value into a previously sorted subset of the list. 39612 39612 36912 13692 12369 3 is sorted. Shift nothing. Insert 9. 3 and 9 are sorted. Shift 9 to the right. Insert 6. 3,6 and 9 are sorted. Shift 9,6 and 3 to the right. Insert 1. 1,3,6 and 9 are sorted. Shift 9,6 and 3 to the right. Insert 2. All values are sorted 16

17. Sorting array of objects public class Student { private String name; private int id; public Student( int id, String name) { this.name = name; this.id = id; } // class Student constructor public int getId( ) { return this.id; } // rest methods. } // class Student int [ ] arr = { 3, 9, 6, 1, 2 }; for (int i = 1; i < arr.length; i++) { int j = i; int a = arr[i]; while ( j > 0 && arr[j-1] > a) { arr[j] = arr[j-1]; j--; } // block while arr[j] = a; } // block fo r Insertion sort of integer array How compare two object values ? 17

18. Sorting array of objects,cont. public static void insertSort( Student [ ] arr) { for (int i = 1; i < arr.length; i++) { Student val = arr[i]; // reference to arr[i] int j = i; while( j>0 && ( arr[j-1].getId( ) > val.getId( ))) { arr[j] = arr [j-1]; j--; } // block while arr[j] = val; } // block for } // insertSort We use only getter methods to access student ID value 18

19. Invoke insertSort method public static void main(String[ ] args) { System.out.print("enter number of student " ); int num = reader.nextInt(); Student [ ] arr = new Student[num]; for( int i = 0; i < num; i++) { System.out.print("enter student ID " ); int id = reader.nextInt(); System.out.print("enter student name " ); String name = reader.next(); arr[i] = new Student( id, name ); } // for insertSort(arr); // invoke insertSort method for( int j = 0; j < num; j++) System.out.println("studID = “ + arr[j].getId()); } // main We use getId() getter method to access j student ID value 19

20. Class StudList - UML StudList int MAX_STUD Student [ ] list int lastPos StudList() void addStud(String name) Student delStud(String name) Student getStud(String name) void printStudList() UML diagram to define class StudList Class name Class variables Class methods Constructor 20

21. Class StudList - implementation public class StudList { public static final int MAX_STUD = 100; private Student [ ] list; // array of Student type private int lastPos; // last free position public StudList() { this.list = new Student[MAX_STUD]; this.lastPos = 0; } // StudList class constructor public void addStud( Student st ) { this.list[ this.lastPos ] = st; this.lastPos++; } // addStud 21 This method adds new student to StudList class.

22. Class StudList – implementation,cont. public Student delStud(String name) { Student st = null; int i = 0; while( i < this.lastPos && this.list[i].getName().compareTo(name) != 0 ) i++; if(i < this.lastPos) { st = this.list[i]; for( int k = i+1; k< this.lastPos; k++ ) this.list[k-1] = this.list[k]; this.lastPos--; this.list[this.lastPos] = null; } return st; } // delStud 22 This method removes the student from StudList class and returns a reference to removed value. If the student does not exist in the class, the method returns null.

23. Class StudList – implementation,cont. public Student getStud( String name ) { Student st = null; int i = 0; while( i< this.lastPos && this.list[i].getName().compareTo(name) !=0 ) i++; if(i < this.lastPos) st = this.list[i]; return st; } // getStud public void printStudList() { for( int i = 0; i< this.lastPos; i++ ) System.out.println( "ID = “ + this.list[i].getId() + " name = “ + this.list[i].getName()); } // printStudList } // class StudList 23 This method returns a reference to a student if his name exists in the StudList class. If the student does not exist in the class, the method returns null.

24. Class StudList – delSdud test public static void main(String[ ] args) { System.out.print( “Enter number of student " ); int num = reader.nextInt( ); StudList stL = new StudList( ); for( int i = 0; i < num; i++) { int id = reader.nextInt(); String name = reader.next(); Student st = new Student(id,name); stL. addStud(st); } // for stL.printStudList( ) ; System.out.print(“Enter student name to delete " ); String nmd = reader.next( ) ; Student d = stL.delStud(nmd); if(d == null) System.out.println( “Student not found !" ); else System.out.println( “Student “ + nmd + “delete" ); stL.printStudList(); } // main 24

25. Class StudList – getStud test public static void main(String[ ] args) { System.out.print( “Enter number of student " ); int num = reader.nextInt( ); StudList stL= new StudList( ); for( int i = 0; i < num; i++) { int id = reader.nextInt(); String name = reader.next(); Student st= new Student( id,name); stL. addStud(st); } // for stL.printStudList( ) ; System.out.print(“Enter student name " ); String nmf = reader.next( ) ; Student f = getStud(nmf); if(f == null) System.out.println( “Student not found ! " ); else System.out.println( “Student “ + nmf + “found" ); } // main 25

26. Self - Referential Classes A self-referential class contains a reference member that refers to a class object of the same class type. public class Node { private int data; private Node nextNode; public Node( int data ) { this.data = data; } // class Node constructor1 public Node( int data,Node nextNode) { this.data = data; this.nextNode = nextNode; } // class Node constructor2 public void setData( int data ) { this.data = data; } First constructor has only one argument for the item; the next field is set to null. Field nextNode references a Node object, an object of the same class. Node object can be created to point to the next Node object. 26

27. Class Node,cont. public int getData() { return this.data; } public void setNext( Node nextNode ) { this.nextNode = nextNode; } public Node getNext() { return this.nextNode; } public String toString() { return " " + this.data.toString(); } } // end class Node Java can link self-referential objects together to form such useful data structures as lists, queues, stacks and trees. This method allows modification of the nextNode field. 27

28. Building a linked list from Node objects Node n = new Node(9); Node n1 = new Node(4,n); Node n2 = new Node(5,n1); Node datanextNode 9null n Node datanextNode 9null Node datanextNode 4 n1n Node datanextNode 5 Node datanextNode 4 Node datanextNode 9null n2n1n 28

29. Building a linked list from Node objects public static void main(String[ ] args) { System.out.print("enter the number of nodes "); int num = reader.nextInt(); // num = 5 System.out.print("enter the data value "); int data = reader.nextInt(); Node n = new Node(data); for( int i = 1; i < num; i++) { System.out.print("enter the data value "); data = reader.nextInt(); n = new Node(data,n); } // for while( n != null ) { String str = n.toString(); System.out.println(str); n = n.getNext(); } //while } // main Input data values: 1 2 3 4 5 Output ? System.out.println(n); 29

30. Inserting a node in a linked list Node datanextNode 7 temp Node datanextNode 7 Node datanextNode 5 n Node datanextNode 4 Node datanextNode 9null Node temp = new Node(7, n.getNext()); n.setNext(temp); temp 30 Inserted Node

31. Deleting a node from a linked list Node datanextNode 5 Node datanextNode 4 Node datanextNode 9null ntemp Node datanextNode 5 Node datanextNode 4 Node datanextNode 9null ntemp Node datanextNode 5 Node datanextNode 4null Node datanextNode 9null ntemp 1.Node temp=n.getNext(); 2.n.setNext( temp.getNext() ); 3.temp.setNext(null); 31

32. Calculate sum in a linked list public static int calcSum( Node n) { int sum = 0; Node currPos = n; // reference to first node while( currPos != null ) { sum = sum + currPos.getData(); currPos = currPos.getNext(); } // while return sum; } // calcSum 32

33. Max value position in a linked list public static Node findMaxPos( Node n) { Node maxPos = n; // searching from this place n = n.getNext(); while(n != null ) { if( n.getData() > maxPos.getData() ) maxPos = n; n = n.getNext(); } // while return maxPos; } // findMaxPos 33

34. What are the differences? public class Node { private int data; private Node nextNode; public Node( int data ) { this.data = data; } public Node(int data,Node nextNode) { this.data = data; this.nextNode = nextNode; } public void setData( int data ) { this.data = data; } public class Node { private String data; private Node nextNode; public Node( String data ) { this.data = data; } public Node(String data,Node nextNode) { this.data = data; this.nextNode = nextNode; } public void setData( String data ) { this.data = data; } 34

35. Genericity ( מנגנון הגנריות ) Genericity is a mechanism to specify the types of objects that a class can work with via parameters passed at declaration-time and evaluated at compile-time. Generic programming is the creation of programming constructs that can be used with many different types. UML diagram to define generic class Node Node private T data private Node nextNode Node(T x) Node( T data, Node nextNode) T getData() Node getNext() Void setData( T data) Void setNext(Node nextNode) String toString() constructors Class variables Class methods T is a place holder (( מחזיק מקום 35

36. Generic class Node public class Node { private T data; private Node nextNode; public Node( T data ) { this.data = data; } // class Node constructor1 public Node(T data, Node nextNode) { this.data = data; this.nextNode = nextNode; } // class Node constructor2 public void setData( T data ) { this.data =data; } 36

37. Generic class Node, cont. public T getData() { return this.data; } public void setNext( Node nextNode ) { this.nextNode = nextNode; } public Node getNext() { return this.nextNode; } public String toString() { return " " + this.data; } } // end class generic Node 37

38. Generic class Node - implementation Node datanextNode pnull Point p = new Point(4.0,5.0)); Node np = new Node (p); String s = “Hello”; Node ns = new Node (s); Point XY 4.05.0 np Node datanextNode snull ns String Hello 38

39. Generic class Node - implementation,cont. np.setNext(new Node (new Point(8.0,9.0))); ns.setNext(new Node (“Java”)); Node datanextNode p Node datanextNode null np Point XY 4.05.0 Point XY 8.09.0 Node datanextNode s Node datanextNode null ns String Hello String Java 39

40. Generic class Node - test public static void main(String[ ] args) { System.out.print( "enter number of student " ); int num = reader.nextInt( ); // num=4 System.out.print("enter the name "); String name = reader.next(); Node ns = new Node (name); Node startPos = ns; // help variable for(int i =1; i < num; i++) { System.out.print("enter the name "); name = reader.next(); ns.setNext(new Node (name)); ns = ns.getNext(); } // for printClass(startPos); // recursive method (next slide) } // main 40

41. Linked list – recursion 1 public static void printClass(Node s) { System.out.print(s.getData()); if(s.getNext() != null) { System.out.print(" -> "); printClass(s.getNext()); } } // printClass Input: Ofir Galit David Ronit Output: Ofir -> Galit -> David -> Ronit Base case 41

42. Linked list – recursion 2 42 public static int getClassLength(Node s) { if(s.getNext( ) == null) return 1; return 1 + getClassLength(s.getNext( )); } // getClassLenght Base case Recursive method getClassLength returns the length of linked list.

43. Linked list – recursion 3 public static Node getXposition(Node pos, int x) { if( pos.getData( ) == x ) return pos; if( pos.getNext( ) == null ) return null; return getXposition( pos.getNext( ), x); } // getPosition Base case Recursive method getXposition returns the reference to integer X value position in the linked list ( null if not found).