Emacs org-mode with Java syntax highlighting?

The only mechanism of which I'm aware that supports syntax-highlighted code blocks in Org-mode is the source code block feature you have already mentioned.

Setting org-src-fontify-natively to t should enable syntax highlighting for such blocks:

(setf org-src-fontify-natively t)

Code blocks should look something like this:

* Pretty sweet Org heading

  This is an org-mode file, which is cool for lots of reasons, e.g.

  - it's Emacs, and
  - it supports syntax-highlighted blocks
    - (note that this requires the variable ~org-src-fontify-natively~
      to be set to ~t~)

#+BEGIN_SRC java
  public class HelloWorld {
      public static void main(String[] args) {
          System.out.println("Hello, World");
      }
  }
#+END_SRC

A few tips:

• The quickest way to start a new code block is to type <s and then hit Tab. This expands to

  #+BEGIN_SRC |
  
  #+END_SRC
  

  with the cursor represented by |, so you can just type java and start editing.

• With point inside such a block, org-edit-special, bound to C-c ' by default, will open the code block up in a separate buffer with the appropriate major mode active. You can use the full power of that mode, then type C-c ' again to update the embedded snippet.