Java is mature. It’s tested. And it’s fast (contrary to what the
anti-Java crowd may still claim). It’s also quite verbose. Going from
Java to Ruby, expect your code size to shrink down considerably. You can
also expect it to take less time to knock together quick prototypes.

### Similarities

As with Java, in Ruby,...

* Memory is managed for you via a garbage collector.
* Objects are strongly typed.
* There are public, private, and protected methods.
* There are embedded doc tools (Ruby’s is called RDoc). The docs
  generated by rdoc look very similar to those generated by javadoc.

### Differences

Unlike Java, in Ruby,...

* You don’t need to compile your code. You just run it directly.
* There are several different popular third-party GUI toolkits. Ruby
  users can try [WxRuby][1], [FXRuby][2], [Ruby-GNOME][3],
  or [Ruby Tk](https://github.com/ruby/tk) for example.
* You use the `end` keyword after defining things like classes, instead
  of having to put braces around blocks of code.
* You have `require` instead of `import`.
* All member variables are private. From the outside, you access
  everything via methods.
* Parentheses in method calls are usually optional and often omitted.
* Everything is an object, including numbers like 2 and 3.14159.
* There’s no static type checking.
* Variable names are just labels. They don’t have a type associated with
  them.
* There are no type declarations. You just assign to new variable names
  as-needed and they just “spring up” (i.e. `a = [1,2,3]` rather than
  `int[] a = {1,2,3};`).
* There’s no casting. Just call the methods. Your unit tests should tell
  you before you even run the code if you’re going to see an exception.
* It’s `foo = Foo.new("hi")` instead of `Foo foo = new Foo("hi")`.
* The constructor is always named “initialize” instead of the name of
  the class.
* You have “mixins” instead of interfaces.
* YAML tends to be favored over XML.
* It’s `nil` instead of `null`.
* `==` and `equals()` are handled differently in Ruby. Use `==` when you
  want to test equivalence in Ruby (`equals()` in Java). Use `equal?()`
  when you want to know if two objects are the same (`==` in Java).



[1]: https://github.com/mcorino/wxRuby3
[2]: https://github.com/larskanis/fxruby
[3]: https://ruby-gnome.github.io/