1. This is not recommended to use non-public methods: they might change at any time without notice and your code would stop working after PRPC update.

2. Try to find public method which would do what you need: use http://<yourhost>/prhelp/javadocs/index.html for API documentation. You may also click Recources->Engine API from developer studio.

3. If you insist on your question, try the below code from java step or function. You may go deeper - google Java reflection.

 // Print methods of com.pega.pegarules.priv class
 oLog.error("com.pega.pegarules.priv methods");
 for (Class < ? > c = Class.forName("com.pega.pegarules.priv"); c != null; c = c.getSuperclass()) {
  methods = c.getDeclaredMethods();
  for (int i = 0; i < methods.length; i++) {
   method = methods[i];
   oLog.error("c.getName + method.getName: " + c.getName() + "." + method.getName());
   oLog.error("---params---");
   paramTypes = method.getParameterTypes();
   for (int j = 0; j < paramTypes.length; j++) {
    oLog.error("params: " + paramTypes[j].getName());
   }
  }
 }