Index: src/main/java/java/util/regex/JointSet.java =================================================================== --- src/main/java/java/util/regex/JointSet.java (revision 561776) +++ src/main/java/java/util/regex/JointSet.java (working copy) @@ -84,9 +84,11 @@ } public boolean first(AbstractSet set) { - for (java.util.Iterator i = children.iterator(); i.hasNext();) { - if (((AbstractSet) i.next()).first(set)) { - return true; + if(children != null) { + for (java.util.Iterator i = children.iterator(); i.hasNext();) { + if (((AbstractSet) i.next()).first(set)) { + return true; + } } }