CS#180#Problem#Solving#and#ObjectOriented# … # public#class### Fruit{# # public#String#name;# public#String#color=“Red”;# public#int#type;# # publicvoid changeColor (String#c){##color=c;}}

CS 180 Problem Solving and Object Oriented Programming Fall 2011

Notes for Week 11: Oct 31-‐Nov 4, 2011

Aditya Mathur Department of Computer Science Purdue University West LafayeMe, IN, USA

hMp://www.cs.purdue.edu/homes/apm/courses/CS180Fall2011/

1.  Layouts, menus, listeners 2.  Methods and parameters 3.  Inheritance 4.  Thread class 5.  Concurrency:

•  Task decomposiTon •  Data decomposiTon

10/31-‐11/1

This Week:

Readings and Exercises for Week 11

Readings: GUI: 13.2, 13.3 Concurrency: 14.1, 14.2, 14.3, 14.4 Method and data hiding: 8.2, 8.3 Inheritance: 11.2, 11.3

Exercises: 9.1, 9.2, 9.3

©Aditya Mathur. CS 180. Fall 2011. Week 11

Announcements

Feast with faculty: Wednesday Nov 2, 2011. 6:30pm. Ford Dining Hall Exam 2: Wednesday November 9, 8-‐10pm. WTHR 200. Review for Exam 2: Monday November 7, 2011 Special class: Sunday November 6, 2011. 4pm. LWSN 3102AB Project 4 available. HW 8 available.


Problem: GUI


Write a Java app that creates the GUI shown below and performs tasks as explained.

buMons

Menu Menu bar

Problem: Menu an Menu items


Menu items

Problem: AcTons


Bird picture

Bird sound

Terminate program

Problem: CreaTng Sounds


import java.applet.*;

AudioClip birdClip;

import java.net.URL;

try{ birdURL=new URL("file:bird.au"); } catch(ExcepTon e){

} birdClip=Applet.newAudioClip(birdURL);

URL birdURL; Could also be a complete URL

Problem: CreaTng Image Icons


import javax.swing.*;

ImageIcon birdPic// Declare an ImageIcon object;

birdPic=new ImageIcon("bird.jpg”);// Create an icon from a picture;

buMon.setIcon(birdPic);// Add an icon to a buMon

JBuMon buMon=new JBuMon(); Could also be a URL

Live demo


Announcements

Feast with faculty: Wednesday Nov 2, 2011. 6:30pm. Ford Dining Hall Exam 2: Wednesday November 9, 8-‐10pm. WTHR 200. Review for Exam 2: Monday November 7, 2011 Special class: Sunday November 6, 2011. 4pm. LWSN 3102AB


Back to GUIs, Classes, objects, methods!


GUIs: What have we covered so far? •  Widgets: Frame, panel, buMon, text field, label, menu

bar, menu, menu item

•  Listeners: AcTonLsitener, MouseListener, KeyListener •  Layouts: FlowLayout, BorderLayout, GridLayout •  Incremental development: Layout the GUI in steps

starTng with the frame and ending with the listeners.


GUIs: What have we not covered? •  A LOT!

•  There are other widgets, layouts, and listeners that we have not covered and will not be able to cover.

•  There are many methods available with each widget that we have not covered and will not be able to cover.

•  Given what you now know, it should not be difficult to learn more about GUIs on your own!


Instance variables public class Fruit{ public String name; public String color; public int type }


public class Market{ public staTc void main(String [] args){ System.out.println(Fruit.color); } }

Will this compile?

Instance variables public class Fruit{

public String name; public String color=“Red”; public int type; public void changeColor

(String c){ color=c;

} }


public class Market{ public staTc void main(String [] args){ Fruit apple=new Fruit(); Fruit pear=new Fruit(); pear.changeColor(“Green”); System.out.println(apple.color); System.out.println(pear.color); } }

Will this compile?

Class variables public class Fruit{

public String name; public staTc String color; public int type; }


public class Market{ public staTc void main(Strings[] args){ System.out.println(Fruit.color); } }

Will this compile? Yes, because color is staTc and public.

Class: variables public class Fruit{

public String name; public staTc String color; public int type }


public class Market{ public staTc void main(Strings[] args){ Fruit apple=new Fruit(); System.out.println(apple.color); }

Will this compile? Yes, because color will be obtained from Fruit which is the parent class of apple.

Private/Public variables public class Fruit{

public String name; private String color=“Red”; int type; }


public class Market{ public staTc void main(String [] args){ Fruit apple=new Fruit(); Fruit pear=new Fruit(); System.out.println(apple.color); System.out.println(pear.color); } }

Will this compile?

Private/Public variables public class Fruit{

public String name; private String color=“Red”; int type; public void changeColor

(String c){ color=c;

} public String getColor(){

return color; } }


public class Market{ public staTc void main(String [] args){ Fruit apple=new Fruit(); Fruit pear=new Fruit(); pear.changeColor(“Green”); System.out.println(apple.getColor()); System.out.println(pear.getColor()); } }

Will this compile?

Accessor (get) and mutator (set) methods public class Fruit{ public String name; private String color=“Red”; int type; public void changeColor(String c){

color=c; } public String get Color(){

return color; } }


Accessor method

Mutator method

Inheritance


Inheritance: What and Why?


What: A mechanism to create new classes from exisTng classes.

Why: Commonly used stat (variables, objects) and behavior (methods) is encapsulated in one class and can be used by other classes.

Example: JApplet: Your class can extend JApplet and inherit all state and behavior methods in JApplet.

Simple inheritance


Class A

Class B

B inherits from A

Class C

C inherits from B

Class D

D inherits from A

Subclass

Base class

Simple inheritance: Example


Class Vehicle

Class Car

Car inherits from Vehicle

Class MyCar

MyCar inherits from Car

Class RecreaTonalVehicle

RV inherits from Vehicle

MulTple inheritance: Not Allowed in Java!


Class Vehicle

Class Car

Car inherits from Vehicle

Class Engine

and from Engine

Inheritance: Code for a Base class


public class Vehicle{ String manufacturer="Unknown"; int wheels=4; int steering=1; int capacity=4; boolean seatBelts=true; public void drive(){ System.out.print("I am driving."); } public void oilChange(String vehicleName){ System.out.println("Oil changed for "+vehicleName); } }

Inheritance: Code for a subclass


public class Car extends Vehicle{ int capacity=5; // Overridden instance variable int maxSpeed=130; // Added instance variable public void drive(){ // Overridden method System.out.println("This car drives great. I am driving."); } public staTc void main(String[] args){ Car c=new Car(); Vehicle v=new Vehicle(); System.out.println("This car has "+ c.capacity+ " seats."); System.out.println("This vehicle has a seaTng capacity of "+ v.capacity+"."); System.out.println("This car has seat belts:"+ c.seatBelts); } }

Inheritance


public class Fruit{ public String name; private String color=“Red”; int type; public void changeColor

(String c){ Color=c;

} public String getColor(){

return color; } }

public class Mango extends Fruit{ public String origin; public void harvest(){

} public String getOrigin(){

return color; } }

All methods and local variables/objects are available to Mango.

Inheritance: Another example


public class Gui extends JFrame{ }

All methods and local variables/objects of JFrame are available to Gui.

Accessibility rules: Let us fill this table


Modifier Class Package Subclass World

public Y Y Y Y

private Y N N N

None (package private)

Y Y Y/N N

If a variable or an object declaraTon uses this modifier

then can this variable or object be used inside ?

Package: A collecTon of classes idenTfied as a Java package. World: CollecTon of packages

Y: Yes. N: No.

Classes etc.: summary


Base class: Any class, not final, can serve as a base class

Sub class: A class that extends another class

Interface: Not a class but a contract; must be implemented in full before use

Abstract class: Must be extended for use; may contain some methods with implementaTon (concrete methods) and others to be implemented (abstract methods).

Concurrent Programming


Dividing work into small segments


class

Instance variables Class variables Methods

class


class


Program

Concurrency


T

T1 T2 TN . . . .

T

Main thread controls the distribuTon of work

N threads execuTng concurrently to execute N tasks T1, T2…TN.

Distribute work

Task T is divided into N simpler tasks and executed in parallel

Threads


•  Thread is a class

•  A thread is a sequence of computaTons that can run in parallel with other threads.

•  One uses the Thread class to create a thread.

Problem


•  Given doubles x and y and a boolean z, write a program to compute the following

sin(x)/cos(y)+(x2+y2); if z is true sin(x)/cos(y)+(x2 -‐ y2); if z is false

Problem: SoluTon architecture


T

T1 T2

T

T: Perform the given task

T1: Compute a part of the expression

T2: Compute a other part of the expression

Combine the results of T1 and T2

How many threads?

Problem: Algorithm


Thread A: Input: x and y

Compute sin(x)/cos(y)

Thread B: Input: x, y, z

Compute x2+y2 if z is true or x2-‐y2 if z is false

Thread C (control thread): •  Input: x , y, z; •  Create an object e1(Thread A ); •  Create can object e2(Thread B); •  Start e1; •  Start e2; •  Wait for e1 and e2 to complete; •  Get value computed by e1; •  Get value computed by e2; •  Add the two values and display the

result;

Problem: Program


Week 11: October 31-‐November 4, 2011 Hope you enjoyed this week!

QuesTons?

Contact your recitaTon instructor. Make

full use of our office hours.


Documents

CS#180#Problem#Solving#and#ObjectOriented# … # public#class### Fruit{# # public#String#name;# public#String#color=“Red”;# public#int#type;# # publicvoid changeColor (String#c){##color=c;}}