improve java dependency detection

tests/samples/codefiles/java.java

@@ -0,0 +1,20 @@
+// Hello.java
+import java.io.*;
+import static java.lang.Math.*;
+import static com.googlecode.javacv.jna.highgui.cvReleaseCapture;
+import javax.servlet.*;
+import com.colorfulwolf.webcamapplet.gui.ImagePanel;
+import com.foobar.*;
+
+public class Hello extends GenericServlet {
+    public void service(final ServletRequest request, final ServletResponse response)
+    throws ServletException, IOException {
+        response.setContentType("text/html");
+        final PrintWriter pw = response.getWriter();
+        try {
+            pw.println("Hello, world!");
+        } finally {
+            pw.close();
+        }
+    }
+}