总结日期对象和字符串之间转换的常用方法
1、获取日期对象的毫秒数
用日期变量调用getTime方法，返回Long型
2、将字符串转换成日期对象
先使用SimpleDateFormat类的构造方法，传入指定规则，创建日期格式化实例
然后使用该实例调用parse方法，将字符串转换成日期类型
常用的日期格式：yyyy-MM-dd HH:mm:ss
3、将日期对象转换成字符串
先使用SimpleDateFormat类的构造方法，传入指定规则，创建日期格式化实例
然后使用该实例调用format方法，将日期类型转换成字符串
4、比较日期对象
日期1.compareTo(日期2)
相等，返回0; 日期1早于日期2返回-1，日期1晚于日期2返回1
实例演示：
package com.sc.date;
import com.github.crab2died.exceptions.TimeMatchFormatException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.regex.Pattern;
public class DateUtil {
public static final String DATE_FORMAT_DAY = "yyyy-MM-dd";
public static final String DATE_FORMAT_DAY_2 = "yyyy/MM/dd";
public static final String TIME_FORMAT_SEC = "HH:mm:ss";
public static final String DATE_FORMAT_SEC = "yyyy-MM-dd HH:mm:ss";
public static final String DATE_FORMAT_MSEC = "yyyy-MM-dd HH:mm:ss.SSS";
public static final String DATE_FORMAT_MSEC_T = "yyyy-MM-dd'T'HH:mm:ss.SSS";
public static final String DATE_FORMAT_MSEC_T_Z = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
public static final String DATE_FORMAT_DAY_SIMPLE = "y/M/d";
/**
* 匹配yyyy-MM-dd
*/
private static final String DATE_REG = "^[1-9]\\d{3}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])$";
/**
* 匹配yyyy/MM/dd
*/
private static final String DATE_REG_2 = "^[1-9]\\d{3}/(0[1-9]|1[0-2])/(0[1-9]|[1-2][0-9]|3[0-1])$";
/**
* 匹配y/M/d
*/
private static final String DATE_REG_SIMPLE_2 = "^[1-9]\\d{3}/([1-9]|1[0-2])/([1-9]|[1-2][0-9]|3[0-1])$";
/**
* 匹配HH:mm:ss
*/
private static final String TIME_SEC_REG = "^(20|21|22|23|[0-1]\\d):[0-5]\\d:[0-5]\\d$";
/**
* 匹配yyyy-MM-dd HH:mm:ss
*/
private static final String DATE_TIME_REG = "^[1-9]\\d{3}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])\\s" +
"(20|21|22|23|[0-1]\\d):[0-5]\\d:[0-5]\\d$";
/**
* 匹配yyyy-MM-dd HH:mm:ss.SSS
*/
private static final String DATE_TIME_MSEC_REG = "^[1-9]\\d{3}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])\\s" +
"(20|21|22|23|[0-1]\\d):[0-5]\\d:[0-5]\\d\\.\\d{3}$";
/**
* 匹配yyyy-MM-dd'T'HH:mm:ss.SSS
*/
private static final String DATE_TIME_MSEC_T_REG = "^[1-9]\\d{3}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])T" +
"(20|21|22|23|[0-1]\\d):[0-5]\\d:[0-5]\\d\\.\\d{3}$";
/**
* 匹配yyyy-MM-dd'T'HH:mm:ss.SSS'Z'
*/
private static final String DATE_TIME_MSEC_T_Z_REG = "^[1-9]\\d{3}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])T" +
"(20|21|22|23|[0-1]\\d):[0-5]\\d:[0-5]\\d\\.\\d{3}Z$";
/**
* <p>字符串时间转为{@link Date}类型，
* 未找到匹配类型则抛出{@link TimeMatchFormatException}异常</p>
* <p>支持匹配类型列表：</p>
* <p>yyyy-MM-dd</p>
* <p>yyyy/MM/dd</p>
* <p>HH:mm:ss</p>
* <p>yyyy-MM-dd HH:mm:ss</p>
* <p>yyyy-MM-dd'T'HH:mm:ss.SSS</p>
* <p>yyyy-MM-dd'T'HH:mm:ss.SSS'Z'</p>
* <p>
*
* @param strDate 时间字符串
* @return Date {@link Date}时间
* @throws ParseException 异常
*/
public static Date str2Date(String strDate) throws ParseException {
strDate = strDate.trim();
SimpleDateFormat sdf = null;
if (isMatched(strDate, DATE_REG)) {
sdf = new SimpleDateFormat(DATE_FORMAT_DAY);
}
if (isMatched(strDate, DATE_REG_2)) {
sdf = new SimpleDateFormat(DATE_FORMAT_DAY_2);
}
if (isMatched(strDate, DATE_REG_SIMPLE_2)) {
sdf = new SimpleDateFormat(DATE_FORMAT_DAY_SIMPLE);
}
if (isMatched(strDate, TIME_SEC_REG)) {
sdf = new SimpleDateFormat(TIME_FORMAT_SEC);
}
if (isMatched(strDate, DATE_TIME_REG)) {
sdf = new SimpleDateFormat(DATE_FORMAT_SEC);
}
if (isMatched(strDate, DATE_TIME_MSEC_REG)) {
sdf = new SimpleDateFormat(DATE_FORMAT_MSEC);
}
if (isMatched(strDate, DATE_TIME_MSEC_T_REG)) {
sdf = new SimpleDateFormat(DATE_FORMAT_MSEC_T);
}
if (isMatched(strDate, DATE_TIME_MSEC_T_Z_REG)) {
sdf = new SimpleDateFormat(DATE_FORMAT_MSEC_T_Z);
}
if (null != sdf) {
return sdf.parse(strDate);
}
throw new TimeMatchFormatException(
String.format("[%s] can not matching right time format", strDate));
}
/**
* <p>将{@link Date}类型转换为指定格式的字符串</p>
*
* @param date {@link Date}类型的时间
* @param pattern 匹配目标内容
* @return 返回格式化后的时间字符串
*/
public static String date2Str(Date date,String pattern) {
SimpleDateFormat sdf = null;
if ((DATE_FORMAT_DAY.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_DAY);
}
if ((DATE_FORMAT_DAY_2.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_DAY_2);
}
if ((DATE_FORMAT_DAY_SIMPLE.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_DAY_SIMPLE);
}
if ((TIME_FORMAT_SEC.equals(pattern))) {
sdf = new SimpleDateFormat(TIME_FORMAT_SEC);
}
if ((DATE_FORMAT_SEC.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_SEC);
}
if ((DATE_FORMAT_MSEC.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_MSEC);
}
if ((DATE_FORMAT_MSEC_T.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_MSEC_T);
}
if ((DATE_FORMAT_MSEC_T_Z.equals(pattern))) {
sdf = new SimpleDateFormat(DATE_FORMAT_MSEC_T_Z);
}
if (null != sdf) {
return sdf.format(date);
}
throw new TimeMatchFormatException(
String.format("[%s] can not matching right time format", date));
}
/**
* Long 转换成 Date
*/
public static Date long2Date(String str) throws ParseException {
Long str1 = Long.parseLong(str);
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String str2 = simpleDateFormat.format(str1);
return simpleDateFormat.parse(str2);//Wed Jun 06 10:28:15 CST 2018
}
/**
* 比较两个Date是否相等
* 比较日期对象 相等返回0，date1早于date2返回-1，date1晚于date2返回1
*/
public static int compareDate(Date date1,Date date2){
return date1.compareTo(date2);
}
/**
* 获取Date毫秒数
*/
public static String getDateTimes(Date date){
Long date1 = date.getTime();
return date1.toString();
}
/**
* <p>判断内容是否匹配</p>
* @param pattern 匹配目标内容
* @param reg 正则表达式
* @return 返回boolean
*/
public static boolean isMatched(String pattern, String reg) {
Pattern compile = Pattern.compile(reg);
return compile.matcher(pattern).matches();
}
}
测试方法：
public static void main(String[] args) throws ParseException {
String str1="1528252095811";
String str2="2018/6/29";
String str3="2018-06-29 14:12:28";
System.out.println(long2Date(str1));//Wed Jun 06 10:28:15 CST 2018
System.out.println(str2Date(str2));//Fri Jun 29 00:00:00 CST 2018
System.out.println(str2Date(str3));//Fri Jun 29 14:12:28 CST 2018
System.out.println(date2Str(new Date(),DATE_FORMAT_MSEC));//2018-10-24 10:21:14.189
System.out.println(compareDate(long2Date(str1),str2Date(str2)));//-1
System.out.println(getDateTimes(new Date()));//1540347818396
}
输出结果：
Wed Jun 06 10:28:15 CST 2018
Fri Jun 29 00:00:00 CST 2018
Fri Jun 29 14:12:28 CST 2018
2018-10-24 10:23:38.393
-1
1540347818396
