Index: main/org/apache/tools/ant/taskdefs/Available.java
===================================================================
RCS file: /home/cvspublic/jakarta-ant/src/main/org/apache/tools/ant/taskdefs/Available.java,v
retrieving revision 1.10
diff -u -r1.10 Available.java
--- main/org/apache/tools/ant/taskdefs/Available.java	2000/09/14 10:49:54	1.10
+++ main/org/apache/tools/ant/taskdefs/Available.java	2000/09/16 17:48:40
@@ -93,6 +93,14 @@
     }
 
     public void execute() throws BuildException {
+        if (property == null) {
+            throw new BuildException("property attribute is required", location);
+        }
+
+        if (classname == null && file == null && resource == null) {
+            throw new BuildException("At least one of (classname|file|resource) is required", location);
+        }
+
         if ((classname != null) && !checkClass(classname)) return;
         if ((file != null) && !checkFile(file)) return;
         if ((resource != null) && !checkResource(resource)) return;