复杂字符串的的查找替换的实现方法？

怎么用java实现复杂字符串的查找替换啊？把下面的代码中一段复杂字符转为空格。.................需要替换的字符串................
<html>
</head>
<title>管理系统</title>
<link rel="stylesheet" href="/chinataxskskj/common/f1.css" type="text/css">
</head>
<body bgcolor="#FFFFFF" marginwidth="0" leftmargin="0" topmargin="0" background="/chinataxskskj/images/back.gif"  marginheight="0">.................原字符串................
<html>
</head>
<title>管理系统</title>
<link rel="stylesheet" href="/chinataxskskj/common/f1.css" type="text/css">
</head>
<body bgcolor="#FFFFFF" marginwidth="0" leftmargin="0" topmargin="0" background="/chinataxskskj/images/back.gif"  marginheight="0"><style type="text/css">
<!--
.font_j2 {  font-size: 12px; color: #666666}
.fj_1 {
font-size: 12px;
color: #FFFFFF;
}
.style1 {color: #000000}
.style2 {
color: #FF0000;
font-weight: bold;
}
.style3 {color: #666666}-->
</style>
<script language="JavaScript" type="text/JavaScript">
<!--
function MM_reloadPage(init) {  //reloads the window if Nav4 resized
  if (init==true) with (navigator) {if ((appName=="Netscape")&&(parseInt(appVersion)==4)) {
    document.MM_pgW=innerWidth; document.MM_pgH=innerHeight; onresize=MM_reloadPage; }}
  else if (innerWidth!=document.MM_pgW || innerHeight!=document.MM_pgH) location.reload();
}
MM_reloadPage(true);
//-->
</script>