String的不可变性

最新推荐文章于 2025-05-10 11:45:10 发布

bingwangzi1988

最新推荐文章于 2025-05-10 11:45:10 发布

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CC 4.0 BY-SA版权

文章标签： Java JSP HTML

本文链接：https://blog.youkuaiyun.com/bingwangzi1988/article/details/83706239

本文通过一个Java Web示例介绍了如何使用session进行数据管理，并展示了String与StringBuffer在可变性上的区别及其对应用的影响。

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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'MyJsp.jsp' starting page</title>

	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>

  <body>
  	<%	List<String> li = new ArrayList<String>(); 
  		session.setAttribute("user", li);
  	  	li.add("wang");
  	  	List<String> li2; 
  	  	li2 = (List<String>)session.getAttribute("user");
  	  	li2.add("zi");
  		out.write(((List<String>)session.getAttribute("user")).toString());

  		String name1 = "aa";
  		session.setAttribute("aaa", name1);
  		String name2 = (String)session.getAttribute("aaa"); 
  		name2 = "bb";
  		out.write((String)session.getAttribute("aaa"));


                StringBuffer name1 = new StringBuffer("aa");
  		session.setAttribute("aaa", name1);
  		StringBuffer name2 = (StringBuffer)session.getAttribute("aaa"); 
  		name2.append("bb");
  		out.write(((StringBuffer)session.getAttribute("aaa")).toString());
   %>
  </body>
</html>