public interface IActor {

    public void basicAct(float money);

    public void dangerAct(float money);
}

public class Actor implements IActor {

    public void basicAct(float money) {
        System.out.println("Begin basic act, get " + money);
    }

    public void dangerAct(float money) {
        System.out.println("Begin danger act, get " + money);
    }
}

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class Client {

    public static void main(String[] args) {

        final Actor actor = new Actor();

        IActor proxyActor = (IActor) Proxy.newProxyInstance(actor.getClass().getClassLoader(),
                actor.getClass().getInterfaces(), new InvocationHandler() {
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        String name = method.getName();
                        Float money = (Float) args[0];
                        Object rtValue = null;
                        if ("basicAct".equals(name)) {
                            if (money < 2000) {
                                rtValue = method.invoke(actor, money/2);
                            }
                        }
                        if ("dangerAct".equals(name)) {
                            if (money >= 5000) {
                                rtValue = method.invoke(actor, money/2);
                            }
                        }

                        return rtValue;
                    }
                });

        proxyActor.basicAct(8000f);
        proxyActor.dangerAct(50000f);
    }
}