1. UML Basics & Access Modifier

2. Java: UML Diagrams
EVE does Java

3. UML Diagram – Class & Object
A class is described using a rectangle box with three sections.
The top section gives the class name, the middle section describes the fields, and the bottom section describes the methods. The middle and bottom sections are optional, but the top section is required.
An object is described using a rectangle box with two sections.
The top section is required. It gives the object’s name and its defining class. The second section is optional; it indicates the object’s field values.

4. The Access Modifiers
The symbols +, - and # are used to denote, respectively, public, private, and protected modifiers in the UML. The static fields and methods are underlined.

5. The Access Modifiers -- public
public access modifier: the + sign in UML
Fields, methods and constructors declared public (least restrictive) within a public class are accessible by all class in the Java program, whether these classes are in the same package or in another package.
For simplicity, just take package as the file folder in Windows
Note: in one application program, there is only and only one public class
Fields/methods are called Class fields/method/member, i.e., you don’t need to create an instance to use them; the convention is to use the classname.methodName notation

6. The Access Modifiers -- private
private access modifier: the – sign in UML
The private (most restrictive) fields or methods cannot be accessed outside the enclosing/declaring class. To make all fields private, provide public getter/setter methods for them.
The getter is used to set the values of the data fields
The setter is used to change/modifier the fields

7. The Access Modifiers -- protected
protected access modifier: the # sign in UML
Fields, methods and constructors declared protected in a class can be accessed only by subclasses in other packages and by those in the same class even if they are not a subclass of the protected member’s class.

8. The Access Modifiers -- default
default access modifier: without any sign
when no access modifier is present, any class, field, method or constructor are accessible only by classes in the same package.
This is also called the instance members, i.e., must create an instance of the class before the fields/methods can be used
Use the instanceName.method() format

9. What is the Modifier? +constructor()
Public
Private
Final
Protected
Static
Default

10. Good! What is this Modifier? -radius: double
Public
Private
Final
Protected
Static
Default

11. Good! What is this one? + numberOfObjects(): int
Public
Private
Final
Protected
Static
Default

12. Good! What is this one? # aMethod(): void
Public
Private
Final
Protected
Static
Default

13. Answer the following: How do you tell which method is a constructor?
To access private methods, you need
public _______ and ________ methods.
(Also called Accessors and Mutators)
A modifier with no symbol is accessible
only within the same folder or __________.
see
see
see

14. Now let’s build a program
The name of the class will be, of course, Rectangle.
class Rectangle

15. Rectangle class
It has two private or local variables, and a static or global variable that is shared.
class Rectangle {
// Data members
private double width = 1, height = 1;
private static String color = "yellow";

16. Rectangle class
The default constructor (with no parameters) - it will use the initialized values for height, width, and color.
// Constructor public Rectangle() { }

17. The Rectangle constructor needs two doubles.
Rectangle class
// Constructor
public Rectangle(double width, double height) {
this.width = width
this.height = height; }
The Rectangle constructor needs two doubles.
If you wish to use the same name in the parameters (formal and actual) you use this.

18. (Accessors and Mutators)
Rectangle class
public double getWidth() {
return width; }
In order to access or make changes to private variables, you need sets and gets.
(Accessors and Mutators)

19. Rectangle class
public double getWidth() {
return width; }
public double getHeight()
return height;
This is to access a Rectangle object’s height and width after it is constructed.

20. Rectangle class
public static String getColor()
{ return color;
} public static void setColor(String color)
{ Rectangle.color = color; }
Color is static- it can be shared – and changed- with all rectangle objects.

21. Rectangle class
public double getArea() {
return width * height; }
public double getPerimeter()
return 2 * (width + height);
Now we just need the methods to get the area and perimeter of a rectangle object.

22. Now put it all together and compile it.
Rectangle class
class Rectangle { // Data members private double width = 1, height = 1; private static String color = "yellow"; // Constructor public Rectangle() { } // Constructor public Rectangle(double width, double height) { this.width = width; this.height = height; } public double getWidth() { return width; } public double getHeight() { return height; } public static String getColor() { return color; } public static void setColor(String color) { Rectangle.color = color; } public double getArea() { return width * height; } public double getPerimeter() { return 2 * (width + height); } }
Now put it all together and compile it.
Did you get it?

23. To see if it works you now have to create a TestRectangle class.
- which includes main.
public class TestRectangle
{ public static void main(String[] args) {

24. TestRectangle class
Rectangle myRect1 = new Rectangle();
Rectangle myRect2 = new Rectangle(4, 40);
Rectangle myRect3 = new Rectangle(3.5, 35.9)
Let’s create three rectangles, one default and two with different parameters.

25. TestRectangle class
To see if it worked, let’s print out the first one. Compile and run. Get it?
System.out.println("The area of the rectangle is "
+ myRect1.getArea());
System.out.println("The perimeter is "
+ myRect1.getPerimeter());
System.out.println("The color is "
+ myRect1.getColor());

26. TestRectangle class
This is the rectangle object with no parameters. You can print out the height and width if you wish.
The area of a rectangle with width 1.0 and height 1.0 is 1.0
The perimeter of a rectangle is 4.0
The color is yellow

27. Now try the next rectangle using (4,40).
TestRectangle class
Now try the next rectangle using (4,40).
System.out.println("The area of the rectangle is "
+ myRect2.getArea());
System.out.println("The perimeter is "
+ myRect2.getPerimeter());
System.out.println("The color is "
+ myRect2.getColor());

28. Did you get it? TestRectangle class
The area of the rectangle is ÏϧÏThe perimeter is 88.0 ÏϧÏThe color is yellow

29. Let’s try something a little different.
TestRectangle class
Let’s try something a little different.
Set the color for the third rectangle to “red” before you print it out.
myRect3.setColor("red"); System.out.println("The area of the rectangle is " myRect3.getArea()); System.out.println("The perimeter is " myRect3.getPerimeter()); System.out.println("The color is " myRect3.getColor());

30. Did you get it?. TestRectangle class
ÏThe area of the rectangle is ÏϧÏThe perimeter is 78.8 ÏϧÏThe color is red ÏϧÏ

31. oops
Try again
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