Java日期格式

本文概述

• java.text.DateFormat字段
• java.text.DateFormat方法
• Java DateFormat示例：日期转换为字符串
• Java DateFormat示例：字符串到日期

在Java中, 有两种用于格式化日期的类：DateFormat和SimpleDateFormat。

java.text.DateFormat类提供了各种方法, 以独立于语言的方式格式化和解析java中的日期和时间。 DateFormat类是一个抽象类。 java.text.Format是父类, 而java.text.SimpleDateFormat是java.text.DateFormat类的子类。

在Java中, 将日期转换为字符串称为格式化, 反之亦然。换句话说, 格式化是指字符串日期, 而解析是指字符串日期。

java.text.DateFormat字段

protected Calendar calendar
protected NumberFormat numberFormat
public static final int ERA_FIELD
public static final int YEAR_FIELD
public static final int MONTH_FIELD
public static final int DATE_FIELD
public static final int HOUR_OF_DAY1_FIELD
public static final int HOUR_OF_DAY0_FIELD
public static final int MINUTE_FIELD
public static final int SECOND_FIELD
public static final int MILLISECOND_FIELD
public static final int DAY_OF_WEEK_FIELD
public static final int DAY_OF_YEAR_FIELD
public static final int DAY_OF_WEEK_IN_MONTH_FIELD
public static final int WEEK_OF_YEAR_FIELD
public static final int WEEK_OF_MONTH_FIELD
public static final int AM_PM_FIELD
public static final int HOUR1_FIELD
public static final int HOUR0_FIELD
public static final int TIMEZONE_FIELD
public static final int FULL
public static final int LONG
public static final int MEDIUM
public static final int SHORT
public static final int DEFAULT

java.text.DateFormat方法

Java DateFormat示例：日期为字符串

让我们看一下使用java.text.DateFormat类在Java中格式化日期和时间的简单示例。

import java.text.DateFormat;
import java.util.Date;
public class DateFormatExample {
	public static void main(String[] args) {
		Date currentDate = new Date();
		System.out.println("Current Date: "+currentDate);
		String dateToStr = DateFormat.getInstance().format(currentDate);
		System.out.println("Date Format using getInstance(): "+dateToStr);
	}
}

输出：

Current Date: Tue Mar 31 14:37:23 IST 2015
Date Format using getInstance(): 31/3/15 2:37 PM

让我们看看使用java.text.DateFormat类在Java中格式化日期和时间的完整示例。

import java.text.DateFormat;
import java.util.Date;
public class DateFormatExample2 {
	public static void main(String[] args) {
		Date currentDate = new Date();
		System.out.println("Current Date: "+currentDate);

		String dateToStr = DateFormat.getInstance().format(currentDate);
		System.out.println("Date Format using getInstance(): "+dateToStr);

		dateToStr = DateFormat.getDateInstance().format(currentDate);
		System.out.println("Date Format using getDateInstance(): "+dateToStr);

		dateToStr = DateFormat.getTimeInstance().format(currentDate);
		System.out.println("Date Format using getTimeInstance(): "+dateToStr);

		dateToStr = DateFormat.getDateTimeInstance().format(currentDate);
		System.out.println("Date Format using getDateTimeInstance(): "+dateToStr);

		dateToStr = DateFormat.getTimeInstance(DateFormat.SHORT).format(currentDate);
		System.out.println("Date Format using getTimeInstance(DateFormat.SHORT): "+dateToStr);

		dateToStr = DateFormat.getTimeInstance(DateFormat.MEDIUM).format(currentDate);
		System.out.println("Date Format using getTimeInstance(DateFormat.MEDIUM): "+dateToStr);
		
		dateToStr = DateFormat.getTimeInstance(DateFormat.LONG).format(currentDate);
		System.out.println("Date Format using getTimeInstance(DateFormat.LONG): "+dateToStr);
		
		dateToStr = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.SHORT).format(currentDate);
		System.out.println("Date Format using getDateTimeInstance(DateFormat.LONG, DateFormat.SHORT): "+dateToStr);

	}
}

输出：

Current Date: Tue Mar 31 14:37:23 IST 2015
Date Format using getInstance(): 31/3/15 2:37 PM
Date Format using getDateInstance(): 31 Mar, 2015
Date Format using getTimeInstance(): 2:37:23 PM
Date Format using getDateTimeInstance(): 31 Mar, 2015 2:37:23 PM
Date Format using getTimeInstance(DateFormat.SHORT): 2:37 PM
Date Format using getTimeInstance(DateFormat.MEDIUM): 2:37:23 PM
Date Format using getTimeInstance(DateFormat.LONG): 2:37:23 PM IST
Date Format using getDateTimeInstance(DateFormat.LONG, DateFormat.SHORT): 31 March, 2015 2:37 PM

Java DateFormat示例：字符串到日期

让我们看一个简单的示例, 使用java.text.DateFormat类将字符串转换为日期。

import java.text.DateFormat;
import java.util.Date;
public class DateFormatExample3 {
	public static void main(String[] args)throws Exception {
		Date d = DateFormat.getDateInstance().parse("31 Mar, 2015");
		System.out.println("Date is: "+d);
	}
}

输出：

Date is: Tue Mar 31 00:00:00 IST 2015