Index: BooleanClause.java
===================================================================
--- BooleanClause.java	(revision 151205)
+++ BooleanClause.java	(working copy)
@@ -71,6 +71,19 @@
     query = q;
     required = r;
     prohibited = p;
+    if (required) {
+      if (prohibited) {
+        throw new IllegalArgumentException("BooleanClause cannot be required and prohibited");
+      } else {
+         occur = Occur.MUST;
+      }
+    } else {
+      if (prohibited) {
+         occur = Occur.MUST_NOT;
+      } else {
+         occur = Occur.SHOULD;
+      }
+    }
   }
 
   /** Constructs a BooleanClause.