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String 与 Date互转
（1）基于SimpleDateFormat实现：package com.bky.df; import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Date; public class DateLangUtils{
public static void main(String[] args) throws ParseException {
Date nowDate = new Date();
String formatString = "yyyy-MM-dd HH:mm:ss";
String dateString = "2018-12-02 16:33:15";
System.out.println(getString(nowDate, formatString));
System.out.println(getDate(dateString, formatString));
System.out.println(getDatePos(dateString, formatString));
} /**
* 使用SimpleDateFormat格式化Date
*
* @param date
* @param formatString
* @return
*/
public static String getString(Date date, String formatString) {
SimpleDateFormat formatter = new SimpleDateFormat(formatString);
return formatter.format(date);
} /**
* 使用SimpleDateFormat解析日期字符串
*
* @param dateString
* @param formatString
* @return
* @throws ParseException
*/
public static Date getDate(String dateString, String formatString) throws ParseException {
SimpleDateFormat formatter = new SimpleDateFormat(formatString);
return formatter.parse(dateString);
} /**
* 使用SimpleDateFormat解析日期字符串
*
* @param dateString
* @param formatString
* @return
*/
public static Date getDatePos(String dateString, String formatString) {
SimpleDateFormat formatter = new SimpleDateFormat(formatString);
return formatter.parse(dateString, new ParsePosition(0));
}
}（2）使用commons组件实现
import java.text.ParseException;
import java.util.Date; import org.apache.commons.lang3.time.DateFormatUtils;
import org.apache.commons.lang3.time.DateUtils; public static void main(String[] args) throws ParseException {
Date nowDate = new Date();
String formatString = "yyyy-MM-dd HH:mm:ss";
String dateString = "2018-12-02 16:33:15";
System.out.println(DateFormatUtils.format(nowDate, formatString));
System.out.println(DateUtils.parseDate(dateString, formatString));
} -
对日期的相关操作
基于Calendar实现Calendar cal = Calendar.getInstance();
// 设置Calendar时间(1.Date 2.longofmills)
cal.setTime(new Date());
cal.setTimeInMillis(System.currentTimeMillis()); // 设置年月日，时分秒，毫秒
cal.set(Calendar.YEAR, cal.get(Calendar.YEAR));
// Calendar.MONTH 从0开始表示1月，需要转换展示/设置
cal.set(Calendar.MONTH, cal.get(Calendar.MONTH));
cal.set(Calendar.DAY_OF_MONTH, cal.get(Calendar.DAY_OF_MONTH));
// 24小时制
cal.set(Calendar.HOUR_OF_DAY, cal.get(Calendar.HOUR_OF_DAY));
// 12小时制
cal.set(Calendar.HOUR, cal.get(Calendar.HOUR));
cal.set(Calendar.MINUTE, cal.get(Calendar.MINUTE));
cal.set(Calendar.SECOND, cal.get(Calendar.SECOND));
cal.set(Calendar.MILLISECOND, cal.get(Calendar.MILLISECOND)); // 设置与星期相关参数
// 设置当周星期周几(1为星期日,7为星期六)
cal.set(Calendar.DAY_OF_WEEK, cal.get(Calendar.DAY_OF_WEEK));
// 设置当月第几个星期(默认地区是从星期日开始算，以日历计算第几周)
cal.set(Calendar.WEEK_OF_MONTH, cal.get(Calendar.WEEK_OF_MONTH));
// 设置当月第几个星期(设置按当月的天数算第几周，7天一周)
cal.set(Calendar.DAY_OF_WEEK_IN_MONTH, cal.get(Calendar.DAY_OF_WEEK_IN_MONTH));
// 设置一年中第几个星期
cal.set(Calendar.WEEK_OF_YEAR, cal.get(Calendar.WEEK_OF_YEAR)); // 设置当月第一天
cal.set(Calendar.DAY_OF_MONTH, cal.getActualMinimum(Calendar.DAY_OF_MONTH));
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0); // 设置当月最后一天
cal.set(Calendar.DAY_OF_MONTH, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0); - 计算两个时间之差
/**
* 根据需要计算并格式化两个时间之差
*
* @param beforeDate
* @param afterDate
* @param formatPatterns(长度一定要为6,如果不需要则传null)
* eg:new String[]{ "年", null, "天", "时", "分", "秒" }
* @return
*/
public static String formatDistanceDate(Date beforeDate, Date afterDate, String[] formatPatterns) {
if (formatPatterns == null || formatPatterns.length < 6)
return "";
long instance = (afterDate.getTime() - beforeDate.getTime()) / 1000;
StringBuilder dateInstanceFormatBuffer = new StringBuilder();
if (formatPatterns[0] != null) {
long year = instance / (3600l * 24 * 365);
if (year > 0) {
dateInstanceFormatBuffer.append(year);
dateInstanceFormatBuffer.append(formatPatterns[0]);
instance = instance % (3600l * 24 * 365);
}
}
if (formatPatterns[1] != null) {
long month = instance / (3600l * 24 * 30);
if (month > 0) {
instance = instance % (3600l * 24 * 30);
dateInstanceFormatBuffer.append(month);
dateInstanceFormatBuffer.append(formatPatterns[1]);
}
}
if (formatPatterns[2] != null) {
long day = instance / (3600l * 24);
if (day > 0) {
instance = instance % (3600l * 24);
dateInstanceFormatBuffer.append(day);
dateInstanceFormatBuffer.append(formatPatterns[2]);
}
}
if (formatPatterns[3] != null) {
long hour = instance / 3600;
if (hour > 0) {
instance = instance % 3600;
dateInstanceFormatBuffer.append(hour);
dateInstanceFormatBuffer.append(formatPatterns[3]);
}
}
if (formatPatterns[4] != null) {
long min = instance / 60;
if (min > 0) {
dateInstanceFormatBuffer.append(min);
dateInstanceFormatBuffer.append(formatPatterns[4]);
}
}
if (formatPatterns[5] != null) {
long second = instance % 60;
if (second > 0) {
dateInstanceFormatBuffer.append(second);
dateInstanceFormatBuffer.append(formatPatterns[5]);
}
}
return dateInstanceFormatBuffer.toString();
}