W7003 The Basics

Within these castle walls be forged Mavens of Computer Science ...

— Merlin, The Coder

First Steps

• Emacs and Java
• mkdir ~/AP-Practice
• Within this directory, mkdir Hello, World
• Create a new file, HelloWorld.java
  • Names matter - the public class name MUST match the file name
• Compile with javac
• An executable must have an entry point which is a public, static function named main, accepting a single argument, an array of strings.
• Execute with java

Short Cuts

• Compilation and Execution can be combined
• All of this can occur within emacs
• Emacs shortcut and up arrow

Static Typing

• Java is statically typed
• Variables must be declared before they can be used, including the type