--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/sjavac/comp/SmartWriter.java	Sun Aug 17 15:52:32 2014 +0100
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code 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
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.tools.sjavac.comp;
+
+import java.io.*;
+import javax.tools.JavaFileObject;
+
+/**
+ * The SmartWriter will cache the written data and when the writer is closed,
+ * then it will compare the cached data with the old_content string.
+ * If different, then it will write all the new content to the file.
+ * If not, the file is not touched.
+ *
+ *  <p><b>This is NOT part of any supported API.
+ * If you write code that depends on this, you do so at your own
+ * risk.  This code and its internal interfaces are subject to change
+ * or deletion without notice.</b></p>
+ */
+public class SmartWriter extends Writer {
+
+    String name;
+    JavaFileObject file;
+    String oldContent;
+    StringWriter newContent = new StringWriter();
+    PrintWriter stdout;
+    boolean closed;
+    public SmartWriter(JavaFileObject f, String s, String n, PrintWriter pw) {
+        name = n;
+        file = f;
+        oldContent = s;
+        newContent = new StringWriter();
+        stdout = pw;
+        closed = false;
+    }
+
+    public void write(char[] chars, int i, int i1)
+    {
+        newContent.write(chars, i, i1);
+    }
+
+    public void close() throws IOException {
+        if (closed) return;
+        closed = true;
+        String s = newContent.toString();
+        if (!oldContent.equals(s)) {
+            int p = file.getName().lastIndexOf(File.separatorChar);
+            try (Writer writer = file.openWriter()) {
+                writer.write(s);
+            }
+            stdout.println("Writing "+file.getName().substring(p+1));
+        }
+    }
+
+    public void flush() throws IOException {
+    }
+}