--- a/src/share/classes/java/nio/channels/Channels.java	Thu Nov 27 15:44:32 2008 +0100
+++ b/src/share/classes/java/nio/channels/Channels.java	Sat Nov 29 20:55:29 2008 -0800
@@ -65,6 +65,10 @@
 
     private Channels() { }              // No instantiation
 
+    private static void checkNotNull(Object o, String name) {
+        if (o == null)
+            throw new NullPointerException("\"" + name + "\" is null!");
+    }
 
     /**
      * Write all remaining bytes in buffer to the given channel.
@@ -120,6 +124,7 @@
      * @return  A new input stream
      */
     public static InputStream newInputStream(ReadableByteChannel ch) {
+        checkNotNull(ch, "ch");
         return new sun.nio.ch.ChannelInputStream(ch);
     }
 
@@ -138,6 +143,8 @@
      * @return  A new output stream
      */
     public static OutputStream newOutputStream(final WritableByteChannel ch) {
+        checkNotNull(ch, "ch");
+
         return new OutputStream() {
 
                 private ByteBuffer bb = null;
@@ -193,9 +200,7 @@
      * @return  A new readable byte channel
      */
     public static ReadableByteChannel newChannel(final InputStream in) {
-        if (in == null) {
-            throw new NullPointerException();
-        }
+        checkNotNull(in, "in");
 
         if (in instanceof FileInputStream &&
             FileInputStream.class.equals(in.getClass())) {
@@ -270,9 +275,7 @@
      * @return  A new writable byte channel
      */
     public static WritableByteChannel newChannel(final OutputStream out) {
-        if (out == null) {
-            throw new NullPointerException();
-        }
+        checkNotNull(out, "out");
 
         if (out instanceof FileOutputStream &&
             FileOutputStream.class.equals(out.getClass())) {
@@ -357,8 +360,8 @@
                                    CharsetDecoder dec,
                                    int minBufferCap)
     {
-        dec.reset();
-        return StreamDecoder.forDecoder(ch, dec, minBufferCap);
+        checkNotNull(ch, "ch");
+        return StreamDecoder.forDecoder(ch, dec.reset(), minBufferCap);
     }
 
     /**
@@ -393,6 +396,7 @@
     public static Reader newReader(ReadableByteChannel ch,
                                    String csName)
     {
+        checkNotNull(csName, "csName");
         return newReader(ch, Charset.forName(csName).newDecoder(), -1);
     }
 
@@ -425,8 +429,8 @@
                                    final CharsetEncoder enc,
                                    final int minBufferCap)
     {
-        enc.reset();
-        return StreamEncoder.forEncoder(ch, enc, minBufferCap);
+        checkNotNull(ch, "ch");
+        return StreamEncoder.forEncoder(ch, enc.reset(), minBufferCap);
     }
 
     /**
@@ -461,6 +465,7 @@
     public static Writer newWriter(WritableByteChannel ch,
                                    String csName)
     {
+        checkNotNull(csName, "csName");
         return newWriter(ch, Charset.forName(csName).newEncoder(), -1);
     }
 

--- a/test/java/nio/channels/Channels/Basic.java	Thu Nov 27 15:44:32 2008 +0100
+++ b/test/java/nio/channels/Channels/Basic.java	Sat Nov 29 20:55:29 2008 -0800
@@ -22,12 +22,13 @@
  */
 
 /* @test
- * @bug 4417152 4481572 6248930
+ * @bug 4417152 4481572 6248930 6725399
  * @summary Test Channels basic functionality
  */
 
 import java.io.*;
 import java.nio.*;
+import java.nio.charset.*;
 import java.nio.channels.*;
 
 
@@ -50,22 +51,106 @@
         test();
     }
 
+    static void failNpeExpected() {
+        throw new RuntimeException("Did not get the expected NullPointerException.");
+    }
+
     private static void test() throws Exception {
+        //Test if methods of Channels throw NPE with null argument(s)
+        try {
+            Channels.newInputStream((ReadableByteChannel)null);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newOutputStream((WritableByteChannel)null);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
         try {
             ReadableByteChannel channel = Channels.newChannel((InputStream)null);
-
-            throw new RuntimeException("Did not get the expected NullPointerException.");
-        } catch (NullPointerException ne) {
-            // OK. As expected.
-        }
+            failNpeExpected();
+        } catch (NullPointerException ne) {}  // OK. As expected.
 
         try {
             WritableByteChannel channel = Channels.newChannel((OutputStream)null);
+            failNpeExpected();
+        } catch (NullPointerException ne) {}  // OK. As expected.
 
-            throw new RuntimeException("Did not get the expected NullPointerException.");
-        } catch (NullPointerException ne) {
-            // OK. As expected.
-        }
+        WritableByteChannel wbc = new WritableByteChannel() {
+            public int write(ByteBuffer src) { return 0; }
+            public void close() throws IOException { }
+            public boolean isOpen() { return true; }
+        };
+
+        ReadableByteChannel rbc = new ReadableByteChannel() {
+            public int read(ByteBuffer dst) { return 0; }
+            public void close() {}
+            public boolean isOpen() { return true; }
+        };
+
+        try {
+            Channels.newReader((ReadableByteChannel)null,
+                               Charset.defaultCharset().newDecoder(),
+                               -1);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newReader(rbc, (CharsetDecoder)null, -1);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newReader((ReadableByteChannel)null,
+                               Charset.defaultCharset().name());
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newReader(rbc, null);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+
+        try {
+            Channels.newReader(null, null);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newWriter((WritableByteChannel)null,
+                               Charset.defaultCharset().newEncoder(),
+                               -1);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newWriter(null, null, -1);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newWriter(wbc, null, -1);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newWriter((WritableByteChannel)null,
+                               Charset.defaultCharset().name());
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newWriter(wbc, null);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
+        try {
+            Channels.newWriter(null, null);
+            failNpeExpected();
+        } catch (NullPointerException npe) {}
+
 
         try {
             blah = File.createTempFile("blah", null);