• A programming language
• A Virtual Machine
• A technology that powers devices, computer programs, and internet applications.

• Released in 1995
• Targeted embedded systems & web
• Original JDK had 8 packages, over 300 in JDK 7
• Designed for portability, garbage collection, simpilicity
• Video History

 Zombie.java:

 public class Zombie {
     public static void main (String [] args) {
         System.out.println("Brains!");
     }
 }

• Name of class & file must be the same.
  
• Names are case-sensitive in Java.
• One Public class per file.
• The "public main" method is automatically executed

• Open a command line and navigate to the folder where you created Zombie.java.

 > javac Zombie.java

• This creates Zombie.class, a Java byte code file.

 > java Zombie

• This runs your Zombie programming

 > jar cvf Zombies.jar Zombie.class

• This creates a Zombies.jar file
• Jaring is very convenient to distribute & reuse your code

 > java -cp Zombies.jar Zombie

• This runs the Zombie class in the Zombies jar

• Java variables are strongly typed
• Variables are declared using a name
• Variable names start with a letter
• Variable names cannot be reserved keywords
• Variable names are case sensitive
• Java convention is to use camel-cased variable names
• ie. myClass or myVariable
• Variables can represent primitives or references to an actual value (ie. an Object)

• boolean
• char
• byte
• short
• int
• long
• float
• double

• Same as primitive variable declarations.
• Can use Custom Objects or Library Objects.

• Assign to them
• Assign from them
• Pass them into methods
• Use them inside of methods

 Zombie.java:

 public class Zombie {
     public static void main (String [] args) {
          String zombieMsg = "Brains!";
          System.out.println(zombieMsg);
     }
 }

 Zombie.java:

 public class Zombie {
     public static void main (String [] args) {
          String zombieMsg = args[0];
          System.out.println(zombieMsg);
     }
 }

• Compile it

 > javac Zombie.java

• Run it

 > java Zombie "I want brains!"

 Zombie.java:

 public class Zombie {
     public static void main (String [] args) {
          if(args.length > 0) {
               String zombieMsg = args[0];
               System.out.println(zombieMsg);
          } else {
               System.out.println("Enter a zombie message");
          }
     }
 }