Transcript classes - NC FRC Teams wiki

Java Programming
Objectives
 Introduce Software Engineering Concepts
 Introduction to Object Oriented and Java
Programming
 Provide Context for Software in FRC Robotics
 Provide Foundation Interacting with Programming
Team
Agenda
 Introduction
 Philosophy
 Object Oriented
 Java Syntax
 FRC Robotics
 Libraries
 Tele-operated
 Autonomous
Introduction
 Mr. Rich Vitkus
 BS Computer Science at Rensselaer Polytechnic Institute
 Manager of Enterprise Architect, Lowe’s Home Improvement
 3 years FLL, 4th year FTC, 6th year FRC
 Evan Vitkus
 VP Programming
 2 years FLL, 2nd year FTC, 2nd year FRC
Philosophy
 Computers do what you tell them to do, not what you




want them to do.
Different results mean either the software, the
system, or the data has changed
Reuse ideas, libraries, and code.
Test and debug systematically with as much
information as possible.
Programming is not art it is engineering. The
standards and process are essential to success.
Object Oriented
 Consider an airport system in the real world. It
consists of many different parts which work together
to get work done

Control tower, airplane, runways, fuel trucks, security agent, …
 When we build a software systems, some of the
software objects have corresponding names

Class ControlTower, class Airplane, class Runway, …
 Reduces “representation gap” between software
model and solution we are building

Improves comprehension, communication, and predictability
Object Oriented – Real World Object
 Consider an airplane in the airport system. What is
important?
 Real world objects have information

Airplanes have a model number, serial number, speed, altitude
 Real world objects also do things
 Airplanes can land, take off, change speed, turn, …
Object Oriented – Software Object
 Have names corresponding to the real world system
 Class Airplane
 Store information – attributes
 modelNumber, serialNumber, speed, altitude
 Perform actions – methods
 land(), takeOff(), changeSpeed(), turn()
Object Oriented – Software Object
 An object bundles data (attributes) and code to
perform actions (methods) into one, cohesive unit
Airplane
speed
model
land()
takeOff()
//Java source code
class airplane
{
private int speed;
private int model;
public void land()
{
…
}
public void takeOff()
{
…
}
Object Oriented – Project
 Simple dice game
 Each player rolls two dice ten times
 The player rolling seven or more the most times is the winner
Object Oriented – Project
 Identify the real world objects in the game
 Game
 Player
 Die
Object Oriented – Project
 Identify the attributes of each object in the game
 Game


dice
players
 Player

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name
score
 Die

value
Object Oriented – Project
 Identify the methods of each object in the game
 Game

play
 Player



takeTurn
incrementScore
getScore
 Die

roll
Object Oriented – Class and Instance
An object bundles data (attributes) and code to perform
actions (methods) into one, cohesive unit
 Class


Definer: A blueprint that
stores the definition for
instances
Creator: A factory for
creating software objects
of one kind
Die
value
roll()
 Instance




Instantiated (created) by a
class
Occupies space in
computer memory
Retains values of
attributes
Has behavior
die1:Die
value=3
Java Syntax - Attributes
 Java is strongly typed
 Two basic types in Java
 Primitive – int, double, boolean, char, etc


private int value;
Object – created from classes

private Die die1;
 Variables– attributes which can change values
 Constants – attributes which do not change values
 private final int SIDES = 6;
Java Syntax - Methods
 Methods can perform actions, have parameters, and
return values
Public void setName(String playerName)
{
name = playerName;
}
public int roll()
{
value = (int)(Math.random()*SIDES) + 1;
return value;
}
Java Syntax – Control Structures - Conditional
 If statements handle boolean (true or false) conditions
if (i == 3)
doSomething();
if (i == 2)
doSomething();
else
doSomethingElse();
if (i == 3) {
doSomething();
}
else if (i == 2) {
doSomethingElse();
}
else {
doSomethingDifferent();
}
Java Syntax – Control Structures - loops
 Loops repeat a segment of code
// validate a boolean condition then execute
while (i < 10) {
doSomething();
}
// execute then validate a boolean condition (always
// run at least once
do {
doSomething();
} while (i < 10);
// execute a specific number of times
for (int i = 0; i < 10; i++) {
doSomething();
}
Java Syntax – Project
public class Game {
private
private
private
private
private
Player player1;
Player player2;
Die die1;
Die die2;
int score;
public void play()
{
for (int i = 0; i < 10; i++) {
score = die1.roll() + die2.roll();
if (score > 7) {
player1.incrementScore();
}
}
for (int i = 0; i < 10; i++) {
score = die1.roll() + die2.roll();
if (score > 7) {
player2.incrementScore();
}
}
if (player1.getScore() > player2.getScore()) {
System.out.print("Player 1 wins");
}
else {
System.out.print("Player 2 wins");
}
}
}
Agenda
 Introduction
 Philosophy
 Object Oriented
 Java Syntax
 FRC Robotics
 Robot
 Libraries
 Tele-operated
 Autonomous
FRC Robotics – Object Oriented
 Software Objects correspond to Real World Objects
 Reduces “representation gap” between software
model and solution we are building

Improves comprehension, communication, and predictability
 An object bundles data (attributes) and code to
perform actions (methods) into one, cohesive unit
FRC Robotics
 Input
 Process
 Output
Lunacy
 http://robotics.nasa.gov/first/2009kickoff/LunacyF
ull.wmv
Robot – Photo 1
Robot – Photo 2
Robot – Photo 3
FRC Robotics - Libraries
 FRC Javadoc
 http://wbrobotics.com/javadoc/index.html
 import edu.wpi.first.wpilibj.Joystick;
 import edu.wpi.first.wpilibj.RobotDrive;
 import edu.wpi.first.wpilibj.Victor;
 import edu.wpi.first.wpilibj.Servo;
 import edu.wpi.first.wpilibj.Jaguar;
 import edu.wpi.first.wpilibj.Compressor;
 import edu.wpi.first.wpilibj.camera.AxisCamera;
 Getting Started with Java for FRC
 http://www.youtube.com/user/thenewboston
FRC Robotics – Teleoperated
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Human Players control the robot
Software controls the robot
Event Loop
Input

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JoySticks
Sensors
Timer
Camera
 Process

Calculations
 Output
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Speed controllers
Solenoid
FRC Robotics – Teleoperated
 Human Driver and Human Robot
 Eyes open
 Eyes closed
FRC Robotics – Teleoperated
 Pseudo Code
FRC Robotics – Autonomous
 No Human Players
 Software controls the robot
 Input
 Sensors
 Timer
 Camera
 Process
 Calculations
 Output
 Speed controllers
 Solenoid
FRC Robotics – Autonomous
 Human Robot
 Vision
 Touch
 Time
FRC Robotics – Autonomous
 Pseudo Code
FRC Robotics – Questions
FRC Robotics – Appendix
 Slides removed to reduce to 75 minutes
Java Syntax - Methods
 Setters and Getters
 Setters are a public method to set the value of private
attributes
 Getters are a public method to get the value of private
attributes
Player
Public
Public
Public
Public
void setName(String playerName)
String getName()
void setScore(int playerScore)
int getScore()
Object Oriented – Concepts
 Cohesion – strongly related responsibilities of a
software component
 Encapsulation – hide information or details


Attributes are private (only exposed to the class)
Methods are public (exposed to the world)
 Polymorphism – multiple methods with the same
name which operate on different data


print(file)
print(integer)
 Inheritance – a generalization, specialization
hierarchy. Extend or override functionality and data
from a parent (super) class

boy is a human is a mammal
Object Oriented – Project
Plays
Player
Game
Rolls
Has
Die
Dice Game Code - Die
public class Die {
private final int SIDES = 6;
int value;
public int getValue()
{
return value;
}
public int roll()
{
value = (int)(Math.random()*SIDES) + 1;
return value;
}
}
Dice Game Code - Player
public class Player {
private String name;
private int score = 0;
public void takeTurn(Die die1, Die die2)
{
int roll;
score = 0;
public void setName(String playerName)
{
name = playerName;
}
for (int i = 0; i < 10; i++) {
roll = die1.roll() + die2.roll();
if (roll > 7) {
incrementScore();
}
public String getName()
{
return name;
}
}
public int getScore()
{
return score;
}
public void incrementScore()
{
score += 1;
}
}
}
Dice Game Code - Game
public class Game {
private
private
private
private
static
static
static
static
Player player1
Player player2
Die die1 = new
Die die2 = new
= new Player();
= new Player();
Die();
Die();
public static void play()
{
player1.takeTurn(die1, die2);
player2.takeTurn(die1, die2);
if (player1.getScore() > player2.getScore()) {
System.out.print("Player 1 wins " + player1.getScore() + " to " + player2.getScore());
}
else if (player1.getScore() < player2.getScore()){
System.out.print("Player 2 wins " + player2.getScore() + " to " + player1.getScore());
}
else
{
System.out.print("It's a tie " + player2.getScore() + " to " + player1.getScore());
}
}
}
Java Syntax – Control Structures - Conditional
 Switch statements handle multiple cases
switch (ch) {
case 'A':
doSomething(); // Triggered if ch == 'A'
break;
case 'B':
case 'C':
doSomethingElse(); // Triggered if ch == 'B' or ch == 'C'
break;
default:
doSomethingDifferent(); // Triggered in any other case
break;
}
Java Syntax – Arrays
 Arrays are an ordered collection


A dozen eggs
The passengers on an airplane
// one dimensional array
int[] numbers = new int[5];
numbers[0] = 2;
numbers[1] = 5;
int x = numbers[0];
// multi dimensional array
int[][] numbers = new int[3][3];
number[1][2] = 2;