W7003 The Basics
From Coder Merlin
Within these castle walls be forged Mavens of Computer Science ...
— Merlin, The Coder
First Steps[edit]
- 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[edit]
- Compilation and Execution can be combined
- All of this can occur within emacs
- Emacs shortcut and up arrow
- Define keyboard macro with f3 and f4, execute with f4
- CTRL-X, CTRL-S, ALT-SHIFT-&, Up-Arrow, ENTER
Semicolons[edit]
Semicolons are required at the end of each statement
Static Typing[edit]
- Java is statically typed
- Variables must be declared before they can be used, including the type
- Types define the possible values of the variable and the operations that may be performed upon it
