use ant as default program

scope4j/src/main/java/org/extendj/ScopeAnalysis.java

@@ -26,13 +26,14 @@ public class ScopeAnalysis extends Frontend {
    */
   public static void main(String[] args) {
 
-    if (args.length != 1) {
-      System.out.println("usage: SccChecker <directory with java files>");
+    if (args.length > 1 || args.length < 0) {
+      System.out.println("usage: ScopeAnalysis <directory with java files>");
       System.exit(-1);
     }
+    String path = args.length == 1 ? args[0] : "../testprograms/ant";
 
     try {
-      List<String> files = Files.walk(Paths.get(args[2]))
+      List<String> files = Files.walk(Paths.get(path))
           .filter(Files::isRegularFile)
           .filter(x -> x.getFileName().toString().endsWith(".java")).map(Path::toString).collect(Collectors.toList());