日期工具类DateUtils

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package date.util;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import java.util.Date;

public class DateUtils {

static final String formatPattern = "yyyy-MM-dd";

static final String formatPattern_Short = "yyyyMMdd";

/**

* 获取当前日期

* @return

*/

public static String getCurrentDate(){

SimpleDateFormat format = new SimpleDateFormat(formatPattern);

return format.format(new Date());

}

/**

* 获取制定毫秒数之前的日期

* @param timeDiff

* @return

*/

public static String getDesignatedDate(long timeDiff){

SimpleDateFormat format = new SimpleDateFormat(formatPattern);

long nowTime = System.currentTimeMillis();

long designTime = nowTime - timeDiff;

return format.format(designTime);

}

/**

*

* 获取前几天的日期

*/

public static String getPrefixDate(String count){

Calendar cal = Calendar.getInstance();

int day = 0-Integer.parseInt(count);

cal.add(Calendar.DATE,day); // int amount 代表天数

Date datNew = cal.getTime();

SimpleDateFormat format = new SimpleDateFormat(formatPattern);

return format.format(datNew);

}

/**

* 日期转换成字符串

* @param date

* @return

*/

public static String dateToString(Date date){

SimpleDateFormat format = new SimpleDateFormat(formatPattern);

return format.format(date);

}

/**

* 字符串转换日期

* @param str

* @return

*/

public static Date stringToDate(String str){

//str = " 2008-07-10 19:20:00 " 格式

SimpleDateFormat format = new SimpleDateFormat(formatPattern);

if(!str.equals("")&&str!=null){

try {

return format.parse(str);

} catch (ParseException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

return null;

}

//java中怎样计算两个时间如：“21:57”和“08:20”相差的分钟数、小时数 java计算两个时间差小时 分钟 秒 .

public void timeSubtract(){

SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

Date begin = null;

Date end = null;

try {

begin = dfs.parse("2004-01-02 11:30:24");

end = dfs.parse("2004-03-26 13:31:40");

} catch (ParseException e) {

e.printStackTrace();

}

long between = (end.getTime() - begin.getTime()) / 1000;// 除以1000是为了转换成秒

long day1 = between / (24 * 3600);

long hour1 = between % (24 * 3600) / 3600;

long minute1 = between % 3600 / 60;

long second1 = between % 60;

System.out.println("" + day1 + "天" + hour1 + "小时" + minute1 + "分"

+ second1 + "秒");

}

}