java中如何在类中判断客户端操作系统是32位的还是64位的操作系统

这个无法获取。。你只能根据请求的头去分析，一般是分析请求头中的UA，如下：
String userAgent = request.getHeader("user-agent");

/**
* 获取客户端操作系统信息，目前只匹配Win 7、WinXP、Win2003、Win2000、MAC、WinNT、Linux、Mac68k、Win9x
* @param userAgent request.getHeader("user-agent")的返回值
* @return
*/

public static String getClientOS(String userAgent)
{
String cos = "unknow os";

Pattern p = Pattern.compile(".*(Windows NT 6\\.1).*");
Matcher m = p.matcher(userAgent);
if(m.find())
{
cos = "Win 7";
return cos;
}

p = Pattern.compile(".*(Windows NT 5\\.1|Windows XP).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "WinXP";
return cos;
}

p = Pattern.compile(".*(Windows NT 5\\.2).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "Win2003";
return cos;
}

p = Pattern.compile(".*(Win2000|Windows 2000|Windows NT 5\\.0).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "Win2000";
return cos;
}

p = Pattern.compile(".*(Mac|apple|MacOS8).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "MAC";
return cos;
}

p = Pattern.compile(".*(WinNT|Windows NT).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "WinNT";
return cos;
}

p = Pattern.compile(".*Linux.*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "Linux";
return cos;
}

p = Pattern.compile(".*(68k|68000).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "Mac68k";
return cos;
}

p = Pattern.compile(".*(9x 4.90|Win9(5|8)|Windows 9(5|8)|95/NT|Win32|32bit).*");
m = p.matcher(userAgent);
if(m.find())
{
cos = "Win9x";
return cos;
}

return cos;
}

System.getProperty("os.arch");
可以通过数值判断
我的是64位的操作系统，返回值是：amd64

打开“我的电脑”然后按右键，看见属性就点下去，就可以找到