--- old/src/java.base/share/classes/java/text/MessageFormat.java	2017-12-01 12:15:23.467531910 +0530
+++ new/src/java.base/share/classes/java/text/MessageFormat.java	2017-12-01 12:15:23.223409910 +0530
@@ -701,6 +701,10 @@
      *            larger than the number of format elements in the pattern string
      */
     public void setFormat(int formatElementIndex, Format newFormat) {
+
+        if (formatElementIndex > maxOffset) {
+            throw new ArrayIndexOutOfBoundsException(formatElementIndex);
+        }
         formats[formatElementIndex] = newFormat;
     }
 
--- /dev/null	2017-12-01 11:27:04.204000000 +0530
+++ new/test/jdk/java/text/Format/MessageFormat/Bug8187551.java	2017-12-01 12:15:23.755675909 +0530
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2017, 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 8187551
+ * @summary test MessageFormat.setFormat() method to throw AIOOBE on invalid
+ *          index
+ */
+
+import java.text.ChoiceFormat;
+import java.text.MessageFormat;
+import java.util.Arrays;
+
+public class Bug8187551 {
+
+    public static void main(String[] args) {
+
+        //invalid cases ("pattern", "invalid format element index")
+        String[][] invalidCases = {{"The disk \"{1}\" contains {0}.", "2"},
+                {"The disk \"{1}\" contains {0}.", "9"},
+                {"On {1}, there are {0} and {2} folders", "3"}};
+
+        //invalid cases (must throw exception)
+        Arrays.stream(invalidCases).forEach(entry -> testSetFormat(entry[0],
+                Integer.valueOf(entry[1])));
+
+    }
+
+    // test the setFormat method for the given pattern and
+    // format element index
+    private static void testSetFormat(String pattern, int elemIndex) {
+        MessageFormat form = new MessageFormat(pattern);
+
+        double[] fileLimits = {0, 1, 2};
+        String[] filePart = {"no files", "one file", "{0,number} files"};
+        ChoiceFormat fileForm = new ChoiceFormat(fileLimits, filePart);
+
+        boolean AIOOBEThrown = false;
+        try {
+            form.setFormat(elemIndex, fileForm);
+        } catch (ArrayIndexOutOfBoundsException ex) {
+            AIOOBEThrown = true;
+        }
+
+        if (!AIOOBEThrown) {
+            throw new RuntimeException("[FAILED: Must throw" +
+                    " ArrayIndexOutOfBoundsException for" +
+                    " invalid index " + elemIndex + " used in" +
+                    " MessageFormat.setFormat(index, format)]");
+        }
+    }
+
+}