【转载】android 工具类 DateUtil，可以用它方便的进行日期的操作

package com.example.tset;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 * 日期操作工具类.
 * 
 * @author shimiso
 * http://blog.csdn.net/xuduzhoud/article/details/27526177
 */
 
public class DateUtil {
 
    private static final String FORMAT = "yyyy-MM-dd HH:mm:ss";
 
    public static Date str2Date(String str) {
        return str2Date(str, null);
    }
 
    public static Date str2Date(String str, String format) {
        if (str == null || str.length() == 0) {
            return null;
        }
        if (format == null || format.length() == 0) {
            format = FORMAT;
        }
        Date date = null;
        try {
            SimpleDateFormat sdf = new SimpleDateFormat(format);
            date = sdf.parse(str);
 
        } catch (Exception e) {
            e.printStackTrace();
        }
        return date;
 
    }
 
    public static Calendar str2Calendar(String str) {
        return str2Calendar(str, null);
 
    }
 
    public static Calendar str2Calendar(String str, String format) {
 
        Date date = str2Date(str, format);
        if (date == null) {
            return null;
        }
        Calendar c = Calendar.getInstance();
        c.setTime(date);
 
        return c;
 
    }
 
    public static String date2Str(Calendar c) {// yyyy-MM-dd HH:mm:ss
        return date2Str(c, null);
    }
 
    public static String date2Str(Calendar c, String format) {
        if (c == null) {
            return null;
        }
        return date2Str(c.getTime(), format);
    }
 
    public static String date2Str(Date d) {// yyyy-MM-dd HH:mm:ss
        return date2Str(d, null);
    }
 
    public static String date2Str(Date d, String format) {// yyyy-MM-dd HH:mm:ss
        if (d == null) {
            return null;
        }
        if (format == null || format.length() == 0) {
            format = FORMAT;
        }
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        String s = sdf.format(d);
        return s;
    }
 
    public static String getCurDateStr() {
        Calendar c = Calendar.getInstance();
        c.setTime(new Date());
        return c.get(Calendar.YEAR) + "-" + (c.get(Calendar.MONTH) + 1) + "-"
                + c.get(Calendar.DAY_OF_MONTH) + "-"
                + c.get(Calendar.HOUR_OF_DAY) + ":" + c.get(Calendar.MINUTE)
                + ":" + c.get(Calendar.SECOND);
    }
 
    /**
     * 获得当前日期的字符串格式
     * 
     * @param format
     * @return
     */
    public static String getCurDateStr(String format) {
        Calendar c = Calendar.getInstance();
        return date2Str(c, format);
    }
 
    // 格式到秒
    public static String getMillon(long time) {
 
        return new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(time);
 
    }
 
    // 格式到天
    public static String getDay(long time) {
 
        return new SimpleDateFormat("yyyy-MM-dd").format(time);
 
    }
 
    // 格式到毫秒
    public static String getSMillon(long time) {
 
        return new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss-SSS").format(time);
 
    }
     
         
    /*
     输入的是String，格式诸如20120102，实现加一天的功能，返回的格式为String，诸如20120103
     */
    public static String stringDatePlus(String row) throws ParseException{
        String year=row.substring(0, 4);
        String month=row.substring(4,6);
        String day=row.substring(6);
        String date1=year+"-"+month+"-"+day;
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        Date startDate=sdf.parse(date1);
        Calendar cd = Calendar.getInstance();  
        cd.setTime(startDate);
        cd.add(Calendar.DATE, 1);
        String dateStr =sdf.format(cd.getTime());
        String year1=dateStr.substring(0,4);
        String month1=dateStr.substring(5,7);
        String day1=dateStr.substring(8);
        return year1+month1+day1;
    }
     
    /*
     输入的是String，格式诸如20120102，实现减一天的功能，返回的格式为String，诸如20120101
     */
    public static String stringDateDecrease(String row) throws ParseException{
        String year=row.substring(0, 4);
        String month=row.substring(4,6);
        String day=row.substring(6);
        String date1=year+"-"+month+"-"+day;
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        Date startDate=sdf.parse(date1);
        Calendar cd = Calendar.getInstance();  
        cd.setTime(startDate);
        cd.add(Calendar.DATE, -1);
        String dateStr =sdf.format(cd.getTime());
        String year1=dateStr.substring(0,4);
        String month1=dateStr.substring(5,7);
        String day1=dateStr.substring(8);
        return year1+month1+day1;
    }
     
    /*
     输入的格式为String，诸如20120101，返回的格式为String，诸如2012-01-01
     */
    public static String stringDateChange(String date)
    {
        if(date.length()=="20120101".length()){
            String year=date.substring(0, 4);
            String month=date.substring(4,6);
            String day=date.substring(6);
            return year+"-"+month+"-"+day;
        }else{
            return date;
        }
         
         
    }
    /**
     * 日期向后推一天
     * @param date 格式：20120101 
     * @return  20120102
     */
    public static String tonextday(String date){
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-1, day+1);
        Date newdate = calendar.getTime();
        SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");
        String da = format.format(newdate);
        return da;
    }
 
    /**
     * 获取当前日期上一周的开始日期 （周日）
     */
    public static String previousWeekByDate(String date) {
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-1, day);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        if(1 == dayWeek) {
            cal.add(Calendar.DAY_OF_MONTH, -1);
        }
        cal.setFirstDayOfWeek(Calendar.SUNDAY);//设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
        int s = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        cal.add(Calendar.DATE, cal.getFirstDayOfWeek()-s);//根据日历的规则，给当前日期减往星期几与一个星期第一天的差值 
        cal.add(Calendar.WEEK_OF_YEAR, -1);
        String imptimeBegin = sdf.format(cal.getTime());
//      System.out.println("所在周星期日的日期："+imptimeBegin);
        return imptimeBegin;
    }
     
     
    /**
     * 获取当前日期上一周的结束日期 （周六）
     */
    public static String previousWeekEndDayByDate(String date) {
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-1, day);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        if(1 == dayWeek) {
            cal.add(Calendar.DAY_OF_MONTH, -1);
        }
        cal.setFirstDayOfWeek(Calendar.SUNDAY);//设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
        int s = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        cal.add(Calendar.DATE, cal.getFirstDayOfWeek()+(6-s));
        cal.add(Calendar.WEEK_OF_YEAR, -1);
        String imptimeBegin = sdf.format(cal.getTime());
//      System.out.println("星期六的日期："+imptimeBegin);
        return imptimeBegin;
    }
     
     
    /**
     * 获取当前日期当前一周的开始日期 （周日）
     */
    public static String getCurrentWeekFirstDayByDate(String date) {
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-1, day);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        if(1 == dayWeek) {
            cal.add(Calendar.DAY_OF_MONTH, -1);
        }
        cal.setFirstDayOfWeek(Calendar.SUNDAY);//设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
        int s = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        cal.add(Calendar.DATE, cal.getFirstDayOfWeek()-s);//根据日历的规则，给当前日期减往星期几与一个星期第一天的差值 
       
        String imptimeBegin = sdf.format(cal.getTime());
      //  System.out.println("所在周星期日的日期："+imptimeBegin);
        return imptimeBegin;
    }
    /**
     * 获取当前日期当前一周的结束日期 （周六）
     */
    public static String getCurrentWeekEndDayByDate(String date) {
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-1, day);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        if(1 == dayWeek) {
            cal.add(Calendar.DAY_OF_MONTH, -1);
        }
        cal.setFirstDayOfWeek(Calendar.SUNDAY);//设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
        int s = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
        cal.add(Calendar.DATE, cal.getFirstDayOfWeek()+(6-s));
       
        String imptimeBegin = sdf.format(cal.getTime());
        return imptimeBegin;
    }
     
     
/**
 * 返回上一个月的第一天
 * @param date20120304
 * @return  20120201
 */
    public static String previousMonthByDate(String date) {
        // TODO Auto-generated method stub
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-2, 1);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        String imptimeBegin = sdf.format(cal.getTime());
//      System.out.println(imptimeBegin);
        return imptimeBegin;
    }
     
    /**
     * 返回下一个月的第一天
     * @param date20120304
     * @return  20120401
     */
    public static String nextMonthByDate(String date) {
        // TODO Auto-generated method stub
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month, 1);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        String imptimeBegin = sdf.format(cal.getTime());
//      System.out.println(imptimeBegin);
        return imptimeBegin;
    }
/**
 * 返回当前月的第一天 
 * @param date20120103
 * @return 20120101
 */
    public static String getCurrentMonthFirstDayByDate(String date) {
        int year = Integer.parseInt(date.substring(0,4));
        int month = Integer.parseInt(date.substring(4,6));
        int day = Integer.parseInt(date.substring(6));
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month-1, 1);
        Date newdate = calendar.getTime();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd"); 
        Calendar cal = Calendar.getInstance();
        cal.setTime(newdate);
        String imptimeBegin = sdf.format(cal.getTime());
        return imptimeBegin;
    }
     
}