jsp中如何求加几天或减几天的日期？

Question

用java.util.Calendar对象好象有add(int numer,int field)方法,field指的是Calendar.DAY,Calendar.YEAR等，

Answer 1

public void add(int amount,int field){
        java.util.Calendar c=java.util.Calendar.getInstance();
        c.setTime(date);
        c.add(field,amount);
        date.setTime(c.getTime().getTime());
}
//field:java.util.Calendar.DAY_OF_MONTH

Answer 2

java.util.Calendar c=java.util.Calendar.getInstance();
c.add(-2,java.util.Calendar.DAY)

Answer 3

<%@ page import="java.util.Date" %>
<%@ page import="java.util.Calendar" %><%Date nn=new Date();%>
<%String s=request.getParameter("JobType");
String n=request.getParameter("textfield3");
String m=request.getParameter("JobDate");
java.util.Calendar c=java.util.Calendar.getInstance();
c.add(-m,java.util.Calendar.DAY_OF_MONTH);
String sql="select * from employ";
employ.ftime='"+m+"'";
sql=sql+" where "+s+"";
if(n.length()>=2){
sql+="and position='"+n+"'";
}
else{}
sql+="and ftime>='"+c.add(-m,java.util.Calendar.DAY_OF_MONTH)+"'";
out.println(sql);
%>
请高手帮忙找错误阿

Answer 4

<%@ page import="java.util.Date" %>
<%@ page import="java.util.Calendar" %>
<%String s=request.getParameter("JobType");
String n=request.getParameter("textfield3");
String m=request.getParameter("JobDate");
java.util.Calendar c=java.util.Calendar.getInstance();
c.add(-m,java.util.Calendar.DAY_OF_MONTH);
String sql="select * from employ";
sql=sql+" where "+s+"";
if(n.length()>=2){
sql+="and position='"+n+"'";
}
else{}
sql+="and ftime>='"+c.add(-m,java.util.Calendar.DAY_OF_MONTH)+"'";
out.println(sql);
%>
请高手帮忙找错误阿，刚才写错了点，这个才是，谁把帮我把这个解决了就给分了

Answer 5

你应该将m转换成int型，Integer.parseInt（m）

Answer 6

<%@ page import="java.util.Date" %>
<%Date date=new Date();%>
<%String s=request.getParameter("JobType");
String n=request.getParameter("textfield3");
String m=request.getParameter("JobDate");
int b=Integer.parseInt(m)
java.util.Calendar c=java.util.Calendar.getInstance();
c.add(-b,java.util.Calendar.DAY_OF_MONTH);
String sql="select * from employ";
sql=sql+" where "+s+"";
if(n.length()>=2){
sql+="and position='"+n+"'";
}
else{}
sql+="and ftime>='"+c.add(-b,java.util.Calendar.DAY_OF_MONTH)+"'";
out.println(sql);
%>还是不对！它提示这种错误！
type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 4 in the jsp file: /job/ss.jspGenerated servlet error:
    [javac] Compiling 1 source fileD:\java\Tomcat 5.0\work\Catalina\localhost\rongw\org\apache\jsp\job\ss_jsp.java:49: ';' expected
java.util.Calendar c=java.util.Calendar.getInstance();
^
1 error
org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:127)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:351)
org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:415)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:458)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:552)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:291)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
note The full stack trace of the root cause is available in the Tomcat logs.

Answer 7

int b=Integer.parseInt(m)//这里没有分号！仔细点。

Answer 8

Generated servlet error:
    [javac] Compiling 1 source fileD:\java\Tomcat 5.0\work\Catalina\localhost\rongw\org\apache\jsp\job\ss_jsp.java:57: 'void' type not allowed here
sql+="and ftime>='"+c.add(-b,java.util.Calendar.DAY_OF_MONTH)+"'";
     ^
1 error还是出现错误阿，怎么回事哦

Answer 9

你的ftime是什么类型的字段?字符串?改成Date,并且加一句
SimpleDateFormat   sDateFormat=new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
c.add(java.util.Calendar.DAY_OF_MONTH,-b)
sql+="and ftime>='"+sDateFormat.format(c.getTime())+"'";

Answer 10

<%@ page import="java.util.*" %>
<%@ page import="java.sql.*" %>
<%@ page import="java.text.SimpleDateFormat" %>
<%String s=request.getParameter("JobType");
String n=request.getParameter("textfield3");
String m=request.getParameter("JobDate");
try{int b=Integer.parseInt(m);}
catch(NumberFormatException e){b=1;}
java.util.Calendar c=java.util.Calendar.getInstance();
SimpleDateFormat   sDateFormat=new SimpleDateFormat("yyyy-MM-dd");
c.add(java.util.Calendar.DAY_OF_MONTH,-b);
String sql="select * from employ";
sql=sql+" where "+s+"";
if(n.length()>=2){
sql+=" and position='"+n+"'";
}
else{}
sql+=" and ftime>='"+sDateFormat.format(c.getTime())+"'";
out.println(sql);
ResultSet rs=connect.db(sql);
%>
各位高手，它还是要出错误，说是空指针异常！
java.lang.NullPointerException
org.apache.jsp.job.search_jsp._jspService(search_jsp.java:169)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
救救我吧