8081794: ParsePosition getErrorIndex returns 0 for TimeZone parsing problem

Reviewed-by: peytoia, okutsu
Contributed-by: NNaveen Kumar <naveen.ah.kumar@oracle.com>

src/share/classes/java/text/SimpleDateFormat.java

@@ -1722,7 +1722,7 @@ public class SimpleDateFormat extends DateFormat {
             }
             return (start + zoneNames[nameIndex].length());
         }
-        return 0;
+        return -start;
     }
 
     /**

test/java/text/Format/DateFormat/Bug8081794.java

+/*
+ * Copyright (c) 2015, 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 8081794
+ * @summary ParsePosition getErrorIndex should return correct index
+ */
+import java.text.ParsePosition;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.Locale;
+
+public class Bug8081794 {
+
+    public static void main(String[] args) {
+        String date = "13 Jan 2005 21:45:34 ABC";
+        String format = "dd MMM yyyy HH:mm:ss z";
+        ParsePosition pp = new ParsePosition(0);
+        pp.setIndex(0);
+        SimpleDateFormat sd = new SimpleDateFormat(format, Locale.ENGLISH);
+        Date d = sd.parse(date, pp);
+        int errorIndex = pp.getErrorIndex();
+        if (errorIndex == 21) {
+            System.out.println(": passed");
+        } else {
+            System.out.println(": failed");
+            throw new RuntimeException("Failed with wrong index: " + errorIndex);
+        }
+    }
+}