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2 Avon High School Tech Club Agenda Old Business –Delete Files New Business –Week 19 Topics: Intro to HTML/CSS: Questions? Group Executive Committee Website Help Introduction to Python Review Intro to Java

3 Avon High School Tech Club HTML/CSS Class QUESTIONS?

4 Avon High School Tech Club Tech Club Executive Committee Next Year: –Election of Officers President Vice President Secretary Treasurer Send me an with interest

5 Avon High School Tech Club Website Help Two Projects –Non-Profit –Realtor Contact me if you are interested

6 Avon High School Tech Club Upcoming Schedule Today: Intro to Java May 14 th : Intro to C# (Guest Speaker) May 21 st : Embedded Programming May 28 th : TBD

7 Avon High School Tech Club Python review

8 Avon High School Tech Club INTRO TO JAVA

9 Avon High School Tech Club Intro to Java History Brief Overview Installation/Tools Getting Started Examples Resources

10 Avon High School Tech Club Over 17 years old Used in mobile, desktop and enterprise apps Emphasizes code portability Statically typed Runs on multiple platforms (via JVM) Did you know Android is Java-based? Java Overview

11 Avon High School Tech Club More on Java Object-Oriented programming language –How we think about the world (nouns and verbs) Java is the 1st or 2nd most popular, depending on who you ask and when

12 Avon High School Tech Club Java Variables Variable Naming Conventions: –Variable names must start with a lowercase letter –Variable names can’t have spaces in them –Variable names can have numbers in them, but they can’t start with them –Variables can’t have any symbols in them except for an underscore ( the _ character) Achieved in Java using Types

13 Avon High School Tech Club Java Types … called Primitives Java TypeExample bytebyte b = 100;Integer shortshort s = 10000;Integer intint n = 5;Integer longlong ssNum = 999_99_9999L;Integer floatfloat f = (float) 4.5;Decimal doubledouble x = 123.4;Decimal booleanboolean b = false;true or false StringString s = “Hello";Words charchar c = ‘t';Letter

14 Avon High School Tech Club Comparing Java to Python PythonJava

15 Avon High School Tech Club Java Conditionals if(this is true){ do this } else{ do this instead }

16 Avon High School Tech Club Java Conditionals if(x > 10){ System.out.println(“x is big!”); } else{ System.out.println(“x is small!”); } /* System.out.println() just tells Java to print what’s in the quotes. */

17 Avon High School Tech Club Java Loops /* Keep doing this until it isn’t true anymore */ while(this is true){ do domething } /* Or repeat something an exact number of times */ for(counter = 0; counter < 10; counter = counter + 1){ do this every time }

18 Avon High School Tech Club Java Loops /* Find the average of 10 of numbers */ int counter; float sum = 0; for(counter = 0; counter < 10; counter = counter + 1){ sum = sum + nextNumber; } float average = sum / 10; For now, we’ll pretend that nextNumber comes from somewhere

19 Avon High School Tech Club Java Functions/Methods There are many situations where you will write code that you want to use again, executing the same instructions but on a different set of data. This is why we use functions/methods In the System.out.println() example, the String in quotes is the argument. The job of System.out.println() is to print its argument to the screen Arguments can be variables or constants, it depends on the method

20 Avon High School Tech Club Java Functions/Methods Functions/Methods: –Reusable, named chunks of code –You’ve seen a Method already: System.out.println() Methods can take in arguments, represents data that the method will manipulate

21 Avon High School Tech Club Java Functions/Methods Example /* First we must define a method */ int addTwoIntegers(int a, int b){ int sum = a + b; return sum; } Return Type Method Name Arguments Method Body Return Value

22 Avon High School Tech Club Java Functions/Methods Example /* First we must define a method */ int addTwoIntegers(int a, int b){ return a + b; } /* Then we use the method */ addTwoIntegers(10,15); /* 25! */ /* We can treat a method like it is a variable of its return type */ int x = addTwoIntegers(10, 15); /* x is 25 */

23 Avon High School Tech Club Java Programming Tips Increment and Decrement an integer (add or subtract 1) –Instead of x = x + 1 use x++ or ++x (use -- for decrement) –All of the arithmetic operators can be “combined” with an equal sign –Instead of x = x + 12 we can use x += 12 –Also -=, *=, /= –The - sign is used for subtraction as well as negative numbers

24 Avon High School Tech Club Java Programming Tips Equals like assignment vs. equals like comparison –We use = to assign a value to a variable, so how do we ask if something is equal to something else? – == means “is equal to” When you’re “reading” code, you should read “ = ” as “becomes” and “ == ” as “is equal to”

25 Avon High School Tech Club Quiz Time! System.out.println() is an example of a reusable chunk of code called a ________ method

26 Avon High School Tech Club Quiz Time! If we need our code to behave differently depending on some condition, we use the word _____ if

27 Avon High School Tech Club Quiz Time! If we need to repeat an action over and over again but we aren’t sure how many times, we use a _____ loop while

28 Avon High School Tech Club Quiz Time! If we need to repeat an action over and over again and we know how many times, we use a _____ loop for

29 Avon High School Tech Club Quiz Time! True or False: If we want to make a decision based on whether or not a variable is equal to something, we use “=” False We use “==“

30 Avon High School Tech Club Quiz Time! What is wrong with this statement: int x = 2.5; x is an integer but 2.5 is a float/double

31 Avon High School Tech Club Quiz Time! int, double, and float are examples of _____ Types

32 Avon High School Tech Club Quiz Time! What does this block of code do: int i = 0; while(i < 10) { System.out.println(i); i = i + 1; } a.) Print “i” 10 times b.) Prints the numbers c.) Prints the numbers d.) Prints the numbers 0 - 9

33 Avon High School Tech Club GETTING STARTED

34 Avon High School Tech Club Getting Started with Java Download Java Development Kit (JDK) – – oads/jdk7-downloads html Download JDK + NetBeans – Java/NetBeans Quick Start – Tip: Configure PATH

35 Avon High School Tech Club Steps to Creating a Java Application Source Code (.java) Compiler (javac) Bytecode (.class) Execute (java)

36 Avon High School Tech Club Step 1: Source Code class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); }

37 Avon High School Tech Club Step 1: Source Code Every application begins with a class definition class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); }

38 Avon High School Tech Club Step 1: Source Code In the Java programming language, every application must contain a main method, where app starts to execute: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); } The public keyword is called an access modifier, meaning it can be accessed by code outside the class

39 Avon High School Tech Club Step 1: Source Code In the Java programming language, every application must contain a main method, where app starts to execute: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); } The static keyword means main can be called before an object of the class has been created.

40 Avon High School Tech Club Step 1: Source Code In the Java programming language, every application must contain a main method, where app starts to execute: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); } The void keyword tells the compiler main does not return a value.

41 Avon High School Tech Club Step 1: Source Code In the Java programming language, every application must contain a main method, where app starts to execute: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); } The String declares a parameter named args of type String (array)

42 Avon High School Tech Club Step 1: Source Code The last line uses the System class from the core library to print the "Hello World!" message to standard output. class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); }

43 Avon High School Tech Club Step 1: Source Code The last line uses the System class from the core library to print the "Hello World!" message to standard output. class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!"); }

44 Avon High School Tech Club Step 2: Compile Your Code javac HelloWorld.java Provided there are no compilation errors, you should now have a.class file: HelloWorld.class

45 Avon High School Tech Club Step 3: Execute Your Application java HelloWorld Hello World! Holla! You just created your first Java App!

46 Avon High School Tech Club Creating Rich Clients Swing JavaFX/Scene Builder

47 Avon High School Tech Club Resources Java Tutorial – Learning –

48 Avon High School Tech Club Your turn …

49 Avon High School Tech Club Getting Started 1. Download the Java Development Kit (JDK 7) (For Ubuntu: sudo apt-get install openjdk-7-jdk) 2. Open a text editor 3. Write a simple ‘Hello World’ program 4. Save it as “ HelloWorld.java ” 5. Compile it ( javac HelloWorld.java ) 6. Run your program ( java HelloWorld )

50 Avon High School Tech Club PATH on Windows Enter javac at command prompt, if you receive an error, install the JDK If JDK is installed, you may need to set the PATH At the command prompt: set path=%path%;“C:\Program Files\Java\jdk1.7.0_21\bin"

51 Avon High School Tech Club Write Your Own Java Program Write a program that prints the name of your operating system and Java version. Hint: Search for system properties …

52 Avon High School Tech Club Challenge 1 public class SysInfo { public static void main(String[] args) { String nameOS = "os.name"; String javaVersion = "java.version"; System.out.println("\n General System Information"); System.out.println("\n OS Name: " + System.getProperty(nameOS)); System.out.println(" Java Version: " + System.getProperty(javaVersion)); }

53 Avon High School Tech Club Advanced Challenge … Write a program that prints the name of your operating system and Java version, then writes it to a file called sys.info Hint: Search for setProperty and file I/O …

54 Avon High School Tech Club Challenge 2 import java.io.FileOutputStream; import java.io.IOException; import java.util.Properties; public class PropApp { public static void main( String[] args ) { String nameOS = "os.name"; String javaVersion = "java.version"; Properties prop = new Properties();

55 Avon High School Tech Club Challenge 2 try { //set the properties value prop.setProperty("OperatingSystem", System.getProperty(nameOS)); prop.setProperty("JavaVersion", System.getProperty(javaVersion)); //save properties to project root folder prop.store(new FileOutputStream(“sys.info”), null); System.out.println("\n System info stored in sys.info”); } catch (IOException ex) { ex.printStackTrace(); }