--- a/src/java.base/share/classes/java/nio/charset/Charset-X-Coder.java.template	Thu Sep 06 10:49:17 2018 -0700
+++ b/src/java.base/share/classes/java/nio/charset/Charset-X-Coder.java.template	Thu Sep 06 12:10:59 2018 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2018, 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
@@ -189,10 +189,12 @@
                    $replType$ replacement)
     {
         this.charset = cs;
-        if (average$ItypesPerOtype$ <= 0.0f)
+        // Use !(a > 0.0f) rather than (a <= 0.0f) to exclude NaN values
+        if (!(average$ItypesPerOtype$ > 0.0f))
             throw new IllegalArgumentException("Non-positive "
                                                + "average$ItypesPerOtype$");
-        if (max$ItypesPerOtype$ <= 0.0f)
+        // Use !(a > 0.0f) rather than (a <= 0.0f) to exclude NaN values
+        if (!(max$ItypesPerOtype$ > 0.0f))
             throw new IllegalArgumentException("Non-positive "
                                                + "max$ItypesPerOtype$");
         if (average$ItypesPerOtype$ > max$ItypesPerOtype$)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/nio/charset/CharsetDecoder/NaNinCtor.java	Thu Sep 06 12:10:59 2018 -0700
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2018, 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.
+ *
+ * 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.
+ */
+
+/* @test
+ * @bug 8210285
+ * @summary NaN arguments to the constructor should be rejected
+ */
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CoderResult;
+
+public class NaNinCtor {
+
+    public static void main(String[] args) throws Throwable {
+        Charset ascii = Charset.forName("US-ASCII");
+
+        // sanity check
+        new MyDecoder(ascii, 0.5f, 1.5f);
+
+        // various combinations of invalid arguments
+        test(() -> new MyDecoder(ascii, 0.0f, 1.0f));
+        test(() -> new MyDecoder(ascii, 1.0f, 0.0f));
+        test(() -> new MyDecoder(ascii, -1.0f, 1.0f));
+        test(() -> new MyDecoder(ascii, 1.0f, -1.0f));
+        test(() -> new MyDecoder(ascii, Float.NaN, 1.0f));
+        test(() -> new MyDecoder(ascii, 1.0f, Float.NaN));
+        test(() -> new MyDecoder(ascii, 1.5f, 0.5f));
+    }
+
+    static void test(Runnable r) {
+        try {
+            r.run();
+            throw new RuntimeException("IllegalArgumentException not thrown");
+        } catch (IllegalArgumentException expected) {
+        }
+    }
+
+    static class MyDecoder extends CharsetDecoder {
+        public MyDecoder(Charset cs, float avg, float max) {
+            super(cs, avg, max);
+        }
+        protected CoderResult decodeLoop(ByteBuffer in, CharBuffer out) {
+            return null;
+        }
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/nio/charset/CharsetEncoder/NaNinCtor.java	Thu Sep 06 12:10:59 2018 -0700
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2018, 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.
+ *
+ * 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.
+ */
+
+/* @test
+ * @bug 8210285
+ * @summary NaN arguments to the constructor should be rejected
+ */
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.CoderResult;
+
+public class NaNinCtor {
+
+    public static void main(String[] args) throws Throwable {
+        Charset ascii = Charset.forName("US-ASCII");
+
+        // sanity check
+        new MyEncoder(ascii, 0.5f, 1.5f);
+
+        // various combinations of invalid arguments
+        test(() -> new MyEncoder(ascii, 0.0f, 1.0f));
+        test(() -> new MyEncoder(ascii, 1.0f, 0.0f));
+        test(() -> new MyEncoder(ascii, -1.0f, 1.0f));
+        test(() -> new MyEncoder(ascii, 1.0f, -1.0f));
+        test(() -> new MyEncoder(ascii, Float.NaN, 1.0f));
+        test(() -> new MyEncoder(ascii, 1.0f, Float.NaN));
+        test(() -> new MyEncoder(ascii, 1.5f, 0.5f));
+    }
+
+    static void test(Runnable r) {
+        try {
+            r.run();
+            throw new RuntimeException("IllegalArgumentException not thrown");
+        } catch (IllegalArgumentException expected) {
+        }
+    }
+
+    static class MyEncoder extends CharsetEncoder {
+        public MyEncoder(Charset cs, float avg, float max) {
+            super(cs, avg, max);
+        }
+        protected CoderResult encodeLoop(CharBuffer in, ByteBuffer out) {
+            return null;
+        }
+    }
+}