CS 201 Lecture 1 (b) Using an IDE Tarik Booker CS 201: Introduction to Programming California State University, Los Angeles

What we will cover… Basic Java Programming (Review) Creating, Compiling, Executing a Java Program Using an IDE Textpad Eclipse JDK

Creating Compiling, and Executing a Java Program You have to create your own program Make sure it works If it doesn’t compile you will not be able to run it! You can compile and run from a command window!

Compiling and Running a File Write your program Save as.java Type javac filename.java Javac = java compile Compiles to a.class file(s) Run java classname.class Runs this within a JVM (Java Virtual Machine)

The Java Virtual Machine The Java Virtual Machine (JVM) is the runtime environment A virtual computer that runs your environment Runs “around” the CPU Creates a layer between the CPU and the Java Program Java is compiled down to bytecode Not machine language JVM is run between the CPU and the Program Slower than something run directly on the CPU This makes the program portable Different JVM’s for different computers (CPUs)

Programming Style Make sure you do the following: Appropriate Comments Proper Indentation and Spacing Space operators Block Styles Next-line style End of line style

Errors There are three possible errors in java Syntax Errors Problems with spelling Missing characters Runtime Errors Abnormal termination Logic Errors

Using an IDE Use Textpad or Netbeans Eclipse is a very powerful IDE we will cover later Good luck!

Textpad Go to Textpad Download The IDE Officially Shareware (Free to download, should pay)

Textpad (2) Install and then run Textpad will install on your computer.

Compiling and Running Using the Command Line Use a text editor (Whatever you choose) Save the file as.java Open a command window: Click the start button Type in cmd (or look for command window in programs)

Compiling and Running Using the Command Line (2) Use DOS commands to locate your java file Get to the location of your file Type javac filename.java Should be the same name as your class

Compiling and Running Using the Command Line (3) Look at our example: Class name is Hello Filename should be Hello.java When we compile, should result in the class name Hello.class To run the program, we must run the class through the JVM (called “java”) java Hello Note: don’t type in java Hello.class (WRONG)

Compiling and Running Using the Command Line (4) Results:

Compiling and Running Using the Command Line (5) Note: If you just want to use the command javac automatically (without using the path name), you must add the path to the computer path Type in “path” at the command line Gives all folders to look for commands

Compiling and Running Using the Command Line (6) After you install the JDK, add the bin folder to the path To change the system path (Windows), perform these steps: Start the System Control Panel applet (Start - Settings - Control Panel - System). Select the Advanced tab. Click the Environment Variables button. Under System Variables, select Path, then click Edit. Other ways (try Windows version first): After this, you can call javac and java (jvm) directly

Using Eclipse Eclipse is a very powerful IDE that can be used to develop Java programs Very complicated to use at first Complex now, later very convenient Download Install Very large file

Eclipse (2) Creating a new project Instead of creating a new file, you must first create a project Holds all files associated with the program Not as necessary now, effective later File -> New -> Java Project Type demo in the Project Name field Select “Use project folder as root for sources and class files” Puts java and class files in same folder Click Finish

Eclipse (3) Creating a new Class File -> New -> Class Opens New Java Class Wizard Type Welcome Our class name Check option public static void main(String[] args) Click Finish

Eclipse (4) Compiling and Running a Class Right-click the Class in Project Display Select Run -> Java Application In context menu Output is displayed in Console pane