方法一：
package example;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class PrevLogin extends HttpServlet{
     public void service(HttpServletRequest req,HttpServletResponse res) throws IOException{
           boolean prevCookie=false;
           Cookie myCookie=null;
           Cookie[] cookies=req.getCookies();
           String str1="你前一次访问本站在";
           String str2="这是你第一次访问本站!";
           byte[] byte1=str1.getBytes();
           byte[] byte2=str2.getBytes();
           res.setContentType("text/html");
           PrintWriter pw=res.getWriter();

           pw.println("");
           pw.println("");
         if(cookies!=null){
           for(int ctr=0;ctr                if(cookies[ctr].getName().equals("PrevLogin")){
                     prevCookie=true;
                     myCookie=cookies[ctr];
                 }
            }
         }
            if(prevCookie){
                pw.println(new String(byte1,"8859_1"));
                pw.println(myCookie.getValue());
                Calendar c1=Calendar.getInstance();
                Date dt=c1.getTime();
                String date=dt.toString();
                myCookie.setValue(date);
                res.addCookie(myCookie);
                prevCookie=false;
            }else{
                    pw.println(new String(byte2,"8859_1"));
                    Calendar c1=Calendar.getInstance();
                    Date dt=c1.getTime();
                    String date=dt.toString();
                    myCookie=new Cookie("PrevLogin",date);
                    res.addCookie(myCookie);
            }
         pw.println("");
         pw.println("");
     }
} 

方法二：

package example;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class PrevLogin extends HttpServlet{
     public void service(HttpServletRequest req,HttpServletResponse res) throws IOException{
           boolean prevCookie=false;
           Cookie myCookie=null;
           Cookie[] cookies=req.getCookies();
           String str1="你前一次访问本站在";
           String str2="这是你第一次访问本站!";
           //方法二
           res.setContentType("text/html;charset=UTF-8");
           req.setCharacterEncoding("UTF-8"); 

           PrintWriter pw=res.getWriter();

           pw.println("");
           pw.println("");
         if(cookies!=null){
           for(int ctr=0;ctr                if(cookies[ctr].getName().equals("PrevLogin")){
                     prevCookie=true;
                     myCookie=cookies[ctr];
                 }
            }
         }
            if(prevCookie){
                pw.println(str1);
                pw.println(myCookie.getValue());
                Calendar c1=Calendar.getInstance();
                Date dt=c1.getTime();
                String date=dt.toString();
                myCookie.setValue(date);
                res.addCookie(myCookie);
                prevCookie=false;
            }else{
                    pw.println(str2);
                    Calendar c1=Calendar.getInstance();
                    Date dt=c1.getTime();
                    String date=dt.toString();
                    myCookie=new Cookie("PrevLogin",date);
                    res.addCookie(myCookie);
            }
         pw.println("");
         pw.println("");
     }
}

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