timjstewart / jscratch-mode

An Emacs mode that lets you quickly experiment with Java. When you're done experimenting, you can export the snippet to source files and a Gradle build file.

jscratch-mode

An Emacs major mode that lets you quickly experiment with Java.

Installation

Clone the repository and add its directory to your load path:

    (add-to-list 'load-path "~/path/to/clone")

Load the library:

    (require 'jscratch-mode)

Auto Insert Snippet

Add the following to your init file:

    (require 'autoinsert)

    (auto-insert-mode t)

    (setq auto-insert-directory "~/.emacs.d/templates/")
    (setq auto-insert-query nil)
    (define-auto-insert "\.jscratch" "jscratch-template.jscratch")

Then create a file named: ~/.emacs.d/templates/jscratch-template.jscratch containing the following:

    /// main: Main
    /// source: Main.java
    /// args: Hello World
    /// jar: com.google.guava:guava:17.0

    public class Main {
        public static void main(final String[] args) {
        }
    }

Now, whenever you create a new file with .jscratch as the extension, the above template will be automatically inserted.

Usage

Once you've created a new Jscratch buffer (with an extension of .jscratch) you can enter the following kinds of things:

A file directive

    /// source: Main.java

The file directive tells Jscratch that all subsequent lines (up until the next file directive) go into a file with the specified name. I find this feature useful because when I'm doing some exploratory coding, I often don't know how long-lived a class will be and I want to keep the set of files very fluid.

A main class directive

    /// main: Main

The main directive allows you to specify which class' main method should be run when you execute the snippet.

A jar file directive

    /// jar: com.group:artifact-id:1.0.0

If your code depends on a jar file, just add a reference to that jar file (using 'Gradle' notation). Your source files will be compiled and run with any referenced jar files on the class path.

Argument directive

    // args: Hello World!

If you want to have arguments passed to your snippet, add one argument directive per argument.

Java code

Once you've specified a file directive, write any code that you want to go into that file after the file directive.

Key Bindings

• C-c r will run the current snippet
• C-c e will export the current snippet to a directory that must exist

Customization

Run 'M-x customize-apropos RET jscratch' to get a list of things you can customize:

• jscratch-gradle-home - the directory where gradle is installed

Maybe To Do

Things I may end up doing:

• Support Java packages and create directory structures that reflect the packages.
• Figure out what to do about temp directories (reuse them or clean them up)
• Figure out how to handle line numbers in error messages. Does Java have something like the C preprocessor's line pragma?
• Allow users to specify an input file where stdin data is read from