1.問題描述向下轉(zhuǎn)型的應(yīng)用場景是面向接口編程的時候，經(jīng)常需要向下轉(zhuǎn)型。但是向上轉(zhuǎn)型的應(yīng)用場景是什么呢？我看到網(wǎng)上有的說是為了獲取父類的方法，子類也可以訪問父類的方法啊，就算是覆蓋的方法，也可以通過super.方法()來訪問父類的方法啊。2.代碼代碼來源是《深入剖析Tomcat》第二章的代碼。package ex02.pyrmont;import java.net.URL;import java.net.URLClassLoader;import java.net.URLStreamHandler;import java.io.File;import java.io.IOException;import javax.servlet.Servlet;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class ServletProcessor1 {    public void process(Request request, Response response) {        String uri = request.getUri();        String servletName = uri.substring(uri.lastIndexOf("/") + 1);        URLClassLoader loader = null;        try {            // create a URLClassLoader            URL[] urls = new URL[1];            URLStreamHandler streamHandler = null;            File classPath = new File(Constants.WEB_ROOT);            // the forming of repository is taken from the createClassLoader            // method in            // org.apache.catalina.startup.ClassLoaderFactory            String repository = (new URL("file", null,                    classPath.getCanonicalPath() + File.separator)).toString();            // the code for forming the URL is taken from the addRepository            // method in            // org.apache.catalina.loader.StandardClassLoader class.            urls[0] = new URL(null, repository, streamHandler);            loader = new URLClassLoader(urls);        } catch (IOException e) {            System.out.println(e.toString());        }        Class myClass = null;        try {            myClass = loader.loadClass(servletName);        } catch (ClassNotFoundException e) {            System.out.println(e.toString());        }