Adding Java style presubmit check.

tools/android/checkstyle/checkstyle.py

+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Script that is used by PRESUBMIT.py to run style checks on Java files."""
+
+import os
+import subprocess
+
+
+def RunCheckstyle(input_api, output_api, style_file):
+  if not os.path.exists(style_file):
+    file_error = ('  Java checkstyle configuration file is missing: '
+                  + style_file)
+    return [output_api.PresubmitError(file_error)]
+
+  # Filter out non-Java files and files that were deleted.
+  java_files = [x.LocalPath() for x in input_api.AffectedFiles(False, False)
+                if os.path.splitext(x.LocalPath())[1] == '.java']
+  if not java_files:
+    return []
+
+  # Run checkstyle
+  checkstyle_env = os.environ.copy()
+  checkstyle_env['JAVA_CMD'] = 'java'
+  try:
+    check = subprocess.Popen(['checkstyle', '-c', style_file] + java_files,
+                             stdout=subprocess.PIPE, env=checkstyle_env)
+    stdout, _ = check.communicate()
+    if check.returncode == 0:
+      return []
+  except OSError as e:
+    import errno
+    if e.errno == errno.ENOENT:
+      install_error = ('  checkstyle is not installed. Please run '
+                       'build/install-build-deps-android.sh')
+      return [output_api.PresubmitPromptWarning(install_error)]
+
+  # Remove non-error values from stdout
+  errors = stdout.splitlines()
+
+  if errors and errors[0] == 'Starting audit...':
+    del errors[0]
+  if errors and errors[-1] == 'Audit done.':
+    del errors[-1]
+
+  # Filter out warnings
+  errors = [x for x in errors if 'warning: ' not in x]
+  if not errors:
+    return []
+
+  local_path = input_api.PresubmitLocalPath()
+  output = []
+  for error in errors:
+    # Change the full file path to relative path in the output lines
+    full_path, end = error.split(':', 1)
+    rel_path = os.path.relpath(full_path, local_path)
+    output.append('  %s:%s' % (rel_path, end))
+  return [output_api.PresubmitPromptWarning('\n'.join(output))]