Here's my emacs/flymake setup for java with and without a dominating build.xml

gistfile1.txt

(require 'flymake)

;; flymake requires something like this in the build.xml:
  ;; <target name="check-syntax" depends="init" description="check for errors">
  ;;   <javac destdir="${build}" 
  ;;          classpathref="project.class.path" 
  ;;          includeantruntime="false">
  ;;     <src path="${CHK_SOURCES}" />
  ;;     <compilerarg value="-Xlint" />
  ;;   </javac>
    
  ;; </target>


(defun flymake-fixed-get-ant-cmdline (source base-dir)
  (list "ant"
	(list "-file"
	      (concat base-dir "/" "build.xml")

              ;; scan the whole directory. fix this??
	      (concat "-DCHK_SOURCES=" (file-name-directory source)) 

	      "check-syntax")))

(defun my-java-flymake-init ()
  "flymake using build.xml if there is one, otherwise javac with lint"
  (if (locate-dominating-file default-directory "build.xml")
      (flymake-simple-make-init-impl 'flymake-create-temp-with-folder-structure
                                     t nil "build.xml" 'flymake-fixed-get-ant-cmdline)
    (list "javac"  (list "-Xlint:unchecked"
                       (flymake-init-create-temp-buffer-copy
                        'flymake-create-temp-with-folder-structure)))))


(add-to-list 'flymake-allowed-file-name-masks
             '("\\.java$" my-java-flymake-init flymake-simple-cleanup))

;; choose an appropriate compile-command
(add-hook 'java-mode-hook
          (lambda ()
            (add-hook 'java-mode-hook 'flymake-mode-on)
            (if (locate-dominating-file default-directory "build.xml")
                (set (make-local-variable 'compile-command)
                     "ant -s build.xml -e ")
              (if buffer-file-name
                  (set (make-local-variable 'compile-command)
                       (concat "javac -Xlint " (file-name-nondirectory buffer-file-name)))))))