--- a/mxtool/mx.py	Wed Jan 14 16:40:56 2015 +0100
+++ b/mxtool/mx.py	Wed Jan 14 09:52:41 2015 -0800
@@ -1593,9 +1593,21 @@
         p.all_deps(deps, includeLibs=includeLibs, includeJreLibs=includeJreLibs, includeAnnotationProcessors=includeAnnotationProcessors)
     return deps
 
-def _handle_missing_java_home():
+def _handle_lookup_java_home(jdk):
+    return _handle_lookup_jdk(jdk, 'JAVA_HOME', '--java-home', False)
+
+def _handle_lookup_extra_java_homes(jdk):
+    return _handle_lookup_jdk(jdk, 'EXTRA_JAVA_HOMES', '--extra-java-homes', True)
+
+def _handle_lookup_jdk(jdk, varName, flagName, allowMultiple):
+    if jdk != None and jdk != '':
+        return jdk
+    jdk = os.environ.get(varName)
+    if jdk != None and jdk != '':
+        return jdk
+
     if not sys.stdout.isatty():
-        abort('Could not find bootstrap JDK. Use --java-home option or ensure JAVA_HOME environment variable is set.')
+        abort('Could not find bootstrap {0}. Use {1} option or ensure {2} environment variable is set.'.format(varName, flagName, varName))
 
     candidateJdks = []
     if get_os() == 'darwin':
@@ -1613,12 +1625,15 @@
 
     javaHome = None
     if len(candidateJdks) != 0:
-        javaHome = select_items(candidateJdks + ['<other>'], allowMultiple=False)
+        log('Missing value for {0}.'.format(varName))
+        javaHome = select_items(candidateJdks + ['<other>'], allowMultiple=allowMultiple)
         if javaHome == '<other>':
             javaHome = None
+        if javaHome != None and allowMultiple:
+            javaHome = os.pathsep.join(javaHome)
 
     while javaHome is None:
-        javaHome = raw_input('Enter path of bootstrap JDK: ')
+        javaHome = raw_input('Enter path of JDK for {0}: '.format(varName))
         rtJarPath = join(javaHome, 'jre', 'lib', 'rt.jar')
         if not exists(rtJarPath):
             log('Does not appear to be a valid JDK as ' + rtJarPath + ' does not exist')
@@ -1627,9 +1642,9 @@
             break
 
     envPath = join(_primary_suite.mxDir, 'env')
-    if ask_yes_no('Persist this setting by adding "JAVA_HOME=' + javaHome + '" to ' + envPath, 'y'):
+    if ask_yes_no('Persist this setting by adding "{0}={1}" to {2}'.format(varName, javaHome, envPath), 'y'):
         with open(envPath, 'a') as fp:
-            print >> fp, 'JAVA_HOME=' + javaHome
+            print >> fp, varName + '=' + javaHome
 
     return javaHome
 
@@ -1683,13 +1698,8 @@
         if opts.very_verbose:
             opts.verbose = True
 
-        if opts.java_home is None:
-            opts.java_home = os.environ.get('JAVA_HOME')
-        if opts.extra_java_homes is None:
-            opts.extra_java_homes = os.environ.get('EXTRA_JAVA_HOMES')
-
-        if opts.java_home is None or opts.java_home == '':
-            opts.java_home = _handle_missing_java_home()
+        opts.java_home = _handle_lookup_java_home(opts.java_home)
+        opts.extra_java_homes = _handle_lookup_extra_java_homes(opts.extra_java_homes)
 
         if opts.user_home is None or opts.user_home == '':
             abort('Could not find user home. Use --user-home option or ensure HOME environment variable is set.')