Introduction to Java
               Material drawn from [Lewis01, Kjell00, Mancoridis01]
                        Java Basics
                             Java
               • Developed by James Gosling at Sun 
                 Microsystems.  
               • Introduced in 1995.
               • Is one the fastest growing programming 
                 technologies of all time.
     Java                                                                                           1
                                                   Bytecode
                             • Java programs are translated into an intermediate 
                                language called bytecode.
                             • Bytecode is the same no matter which computer 
                                platform it is run on. 
                             • Bytecode is translated into native code that the 
                                computer can execute on a program called the 
                                Java Virtual Machine (JVM).
                             • The Bytecode can be executed on any computer 
                                that has the JVM.  Hence Java’s slogan, “Write 
                                once, run anywhere”.
                                       The Java Environment
                                                                                 Runs on
                                                                                Windows PC
                               Code           Compile           Result          Running JVM
                           Java Program     Java Compiler   Java Bytecode          UNIX
                              (*.java)          javac          (*.class)        Running JVM
                                                                                 Macintosh
                                                                                Running JVM
                                              Installing Java
                             • The Java Development Kit (JDK) is a 
                                collection of software available at no charge 
                                from Sun Microsystems, Inc.  The v1.3 
                                download is available at java.sun.com. 
         Java                                                                                                                                                                                   2
             Sample Java Program
         class Hello {
          public static void main ( String[] args ) {
            System.out.println("Hello World!"); 
          } 
         } 
          Try it yourself (Start a Notepad)
                Notepad
   Java                                                     3
                      Save the Source File
                          Name the File
                  Open a Command Interpreter 
                             Window  
                1.Start up the DOS command prompt
                2.Under the system prompt type cd \temp to get to the 
                 directory where you saved Hello.java
                3. Type command dir, to list the files under the 
                 directory. You should see Hello.java
     Java                                                                                                4