package cn.lnu.generic; import java.util.ArrayList; import java.util.List; public class Demo1 { /** * @param args */ public static void main(String[] args) { List list=new ArrayList(); list.add("abc"); //Integer i=(Integer) list.get(0);//Exception in thread "main" java.lang.ClassCastException: java.lang.String List<String> list2=new ArrayList<String>(); list2.add("mushroom"); String str=list2.get(0); System.out.println(str);//mushroom } }