--- a/NEWS	Fri May 02 10:43:06 2014 -0700
+++ b/NEWS	Fri May 02 14:26:03 2014 -0700
@@ -29,6 +29,7 @@
       dir_in_loadpath
       hgload
       hgsave
+      javachk
       numfields
 
  ** Deprecated functions.

--- a/doc/interpreter/java.txi	Fri May 02 10:43:06 2014 -0700
+++ b/doc/interpreter/java.txi	Fri May 02 14:26:03 2014 -0700
@@ -95,9 +95,11 @@
 @cindex path, removing from classpath
 @DOCSTRING(javarmpath)
 
-The following four functions provide information and control over the interface
+The following functions provide information and control over the interface
 between Octave and the Java Virtual Machine.
 
+@DOCSTRING(javachk)
+
 @DOCSTRING(usejava)
 
 @cindex memory, displaying Java memory status

--- a/scripts/help/__unimplemented__.m	Fri May 02 10:43:06 2014 -0700
+++ b/scripts/help/__unimplemented__.m	Fri May 02 14:26:03 2014 -0700
@@ -672,7 +672,6 @@
   "isjava",
   "isocaps",
   "isstudent",
-  "javachk",
   "ldl",
   "libfunctions",
   "libfunctionsview",

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/java/javachk.m	Fri May 02 14:26:03 2014 -0700
@@ -0,0 +1,151 @@
+## Copyright (C) 2014 Philip Nienhuis
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} javachk (@var{feature})
+## @deftypefnx {Function File} {} javachk (@var{feature}, @var{component})
+## @deftypefnx {Function File} {@var{msg} =} javachk (@dots{})
+## Check for the presence of the Java @var{feature} in the current session
+## and print or return an error message if it is not.
+##
+## Possible features are:
+##
+## @table @asis
+## @item @qcode{"awt"}
+## Abstract Window Toolkit for GUIs.
+##
+## @item @qcode{"desktop"}
+## Interactive desktop is running.
+##
+## @item @qcode{"jvm"}
+## Java Virtual Machine.
+##
+## @item @qcode{"swing"}
+## Swing components for lightweight GUIs.
+## @end table
+##
+## If @var{feature} is supported and:
+##
+## @itemize @bullet
+## @item
+## No output argument is requested:
+##
+## Return an empty string
+##
+## @item
+## An output argument is requested:
+##
+## Return a struct with fields @qcode{"feature"} and @qcode{"identifier"}
+## both empty
+##
+## @end itemize
+##
+## If @var{feature} is not supported and:
+##
+## @itemize @bullet
+## @item
+## No output argument is requested:
+##
+## Emit an error message.
+##
+## @item
+## An output argument is requested:
+##
+## Return a struct with field @qcode{"feature"} set to @var{feature} and
+## field @qcode{"identifier"} set to @var{component}
+##
+## @end itemize
+##
+## The optional input @var{component} will be used in place of @var{feature}
+## in any error messages for greater specificity.
+##
+## @code{javachk} determines if specific Java features are available in an
+## Octave session.  This function is provided for scripts which may alter
+## their behavior based on the availability of Java.  The feature
+## @qcode{"desktop"} is never available as Octave has no Java-based desktop.
+## Other features may be available if Octave was compiled with the Java
+## Interface and Java is installed.
+##
+## @seealso{error, usejava}
+## @end deftypefn
+
+## Author: Philip Nienhuis <prnienhuis at users.sf.net>
+## Created: 2014-04-19
+
+function msg = javachk (feature, component="")
+
+  msg = "";
+  chk = false;
+  switch (feature)
+    ## For each feature, try methods() on a Java class of a feature
+    case "awt"
+      try
+        dum = methods ("java.awt.Frame");
+        chk = true;
+      end_try_catch
+    case "desktop"
+      ## Octave has no Java based GUI/desktop, leave chk = false
+    case "jvm"
+      try
+        dum = methods ("java.lang.Runtime");
+        chk = true;
+      end_try_catch
+    case "swing"
+      try
+        dum = methods ("javax.swing.Popup");
+        chk = true;
+      end_try_catch
+    otherwise
+      error ("javachk: unrecognized feature '%s', can be one of 'awt'|'desktop'|'jvm'|'swing'\n", feature);
+  endswitch
+
+  if (! chk)
+    ## Desired feature not present
+    if (nargout >= 1)
+      msg.message = sprintf ("javachk: %s is not supported", feature);
+      msg.identifier = component;
+    else
+      if (! isempty (component))
+        err = sprintf ("javachk: %s is not supported\n", component);
+      else
+        err = sprintf ("javachk: %s is not supported\n", feature);
+      endif
+      error (err);
+    endif
+  endif
+
+endfunction
+
+
+%!error <javachk: desktop is not supported> javachk ("desktop")
+%!error <Java DESKTOP is not supported> javachk ("desktop", "Java DESKTOP")
+%!test
+%! msg = javachk ("desktop");
+%! assert (msg.message, "javachk: desktop is not supported");
+%! assert (msg.identifier, "");
+%!test
+%! msg = javachk ("desktop", "Java DESKTOP");
+%! assert (msg.message, "javachk: desktop is not supported");
+%! assert (msg.identifier, "Java DESKTOP");
+
+%!testif HAVE_JAVA
+%! assert (javachk ("jvm"), "");
+
+%% Test input validation
+%!error <javachk: unrecognized feature 'foobar'> javachk ("foobar")
+

--- a/scripts/java/module.mk	Fri May 02 10:43:06 2014 -0700
+++ b/scripts/java/module.mk	Fri May 02 14:26:03 2014 -0700
@@ -3,6 +3,7 @@
 java_FCN_FILES = \
   java/javaArray.m \
   java/javaaddpath.m \
+  java/javachk.m \
   java/javaclasspath.m \
   java/javamem.m \
   java/javarmpath.m \

--- a/scripts/java/usejava.m	Fri May 02 10:43:06 2014 -0700
+++ b/scripts/java/usejava.m	Fri May 02 14:26:03 2014 -0700
@@ -43,6 +43,7 @@
 ## @qcode{"desktop"} always returns @code{false} as Octave has no Java-based
 ## desktop.  Other features may be available if Octave was compiled with the
 ## Java Interface and Java is installed.
+## @seealso{javachk}
 ## @end deftypefn
 
 ## Author: Rik Wehbring