如果在JAVA中获得指定时间

如果在JAVA中获得指定时间

import java.util.*;
import java.text.*;

public class Test1 {
public static void main(String [] args){

Scanner s=new Scanner(System.in);
int day=s.nextInt();
Calendar c=Calendar.getInstance();
c.add(Calendar.DAY_OF_MONTH, day);
Date d=c.getTime();
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
System.out.println(sdf.format(d));

}
}

如楼上的，要用到Calendar 类，这个类提供了丰富的方法让你对时间或日期进行操作.

获取毫秒数，减去前几天的总毫秒数再取日期

public static Date getDataByNumDay(Date nowDate,int num){
if(nowDate==null){
nowDate=new Date();
}
if(num<0){
//前几天
nowDate.setDate(nowDate.getDate()-(num*-1));
}else{
//后几天
nowDate.setDate(nowDate.getDate()+num);
}
return nowDate;
}
public static void main(String[] args) {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
Date nowDt=new Date();
System.out.println(format.format(nowDt));
Date dt=getDataByNumDay(nowDt, 3);//获得后3天的日期
System.out.println(format.format(dt));
}

java Club 108092625
获取指定日期建议使用Calendar ，通过Calendar的add方法你可以设置获取当前日期前多少天，后多少天
比如使用下面的工具类：
String currentData= DateTimeUtils.getSystemDate() // 返回当前日期，格式为yyyy-MM-dd
String beforeFiveDays = DateTimeUtils.addDays(currentData, -5); //前五天
String afterFiveDays = DateTimeUtils.addDays(currentData, 5); //后五天
附上一个工具类：
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public final class DateTimeUtil
{
private DateTimeUtil()
{
}
private static String DATE_FORMAT_PATTERN = "yyyyMMdd";
private static String TIME_FORMAT_PATTERN = "HHmmss";

public static Date toDateTime(String source, String pattern)
{
Date date = null;
try
{
SimpleDateFormat dateFormat = new SimpleDateFormat(pattern);
date = dateFormat.parse(source);
}
catch (ParseException e)
{
// nothing
}
return date;
}

public static Date toDate(String source)
{
return toDateTime(source, DATE_FORMAT_PATTERN);
}

public static Date toTime(String source)
{
return toDateTime(source, TIME_FORMAT_PATTERN);
}

public static String convert(String source, String fromPattern, String toPattern)
{
Date date = toDateTime(source, fromPattern);
if (date == null)
{
return null;
}
SimpleDateFormat dateFormat = new SimpleDateFormat(toPattern);
return dateFormat.format(date);
}

public static String addDays(String source, int days)
{
Date date = toDate(source);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.DATE, days);
SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT_PATTERN);
return dateFormat.format(calendar.getTime());
}

public static String addMonth(String source , int months)
{
Date date = toDate(source);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.MONTH, months);
SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT_PATTERN);
return dateFormat.format(calendar.getTime());
}

public static String addYears(String source, int years)
{
Date date = toDate(source);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.YEAR, years);
SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT_PATTERN);
return dateFormat.format(calendar.getTime());
}

public static String getSystemDateTime(String format)
{
Date date = new Date();
SimpleDateFormat simpDate = new SimpleDateFormat(format);
String dateStr = simpDate.format(date);
return dateStr;
}

public static String getSystemDate()
{
return getSystemDateTime(DATE_FORMAT_PATTERN);
}

public static String getSystemTime()
{
return getSystemDateTime(TIME_FORMAT_PATTERN);
}

public static String format(Date date, String pattern)
{
SimpleDateFormat simpDate = new SimpleDateFormat(pattern);
String dateStr = simpDate.format(date);
return dateStr;
}

public static String format(long date, String pattern)
{
Date date2 = new Date(date);
return format(date2, pattern);
}
}

你可以使用Calendar的add方法，大致例子：
//获取一个Calendar对象，默认带的是当前时间，想设置可以使用Set方法
Calendar ca = Calendar.getInstance();
//使用add方法，前面的参数是调整的变量，这里设置的是日期，第二个变量是正数则是往后推，负数是往前推
ca.add(Calendar.DATE,-1);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
//getTime返回的是Date对象，然后SimpleDateFormat进行格式化输出
System.out.println(sdf.format(ca.getTime()));