--- 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;
     }