如何使用日歷將日期字符串轉換為其他格式

Question

我從過時的Date庫更改為Calendar ，我需要比較不同的時間字符串對象。

如何使用Calendar將時間字符串(xx:xx:xx)轉換為完整日期(Tue Feb 03 21:02:25 CET 2015)日(Tue Feb 03 21:02:25 CET 2015) ？

我試過了：

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

public class Test2 {

    public static void main(String[] args) throws ParseException {
        // Date date = new SimpleDateFormat("HH:mm:ss").parse("21:20:00"); // Date ist 1970!
        // System.out.println(date.toString());

        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        SimpleDateFormat sdf2 = new SimpleDateFormat("HH:mm:ss | dd.MM.yy");
        cal.set(cal.YEAR, cal.MONTH, cal.DATE, 21, 20, 00);
        System.out.println(sdf2.format(cal.getTime()));

    }

}

和

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

public class Test2 {

    public static void main(String[] args) throws ParseException {
        // Date date = new SimpleDateFormat("HH:mm:ss").parse("21:20:00"); // Date ist 1970!
        // System.out.println(date.toString());

        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        SimpleDateFormat sdf2 = new SimpleDateFormat("HH:mm:ss | dd.MM.yy");
        cal.setTime(sdf.parse("21:20:00"));
        cal.set(Calendar.YEAR, Calendar.MONTH, Calendar.DATE);
        System.out.println(sdf2.format(cal.getTime()));

    }

}

但是他們分別返回： 21:20:00 | 05.03.01 : 21:20:00 | 05.03.01 : 21:20:00 | 05.03.01 21:20:00 | 05.03.01

我希望能夠將結果與其他“完整日期對象”進行比較，例如Tue Feb 03 21:02:25 CET 2015 。

Answer 1

更新過的：

// Set the time in String
String stringDate = "04:10:13";
// Parse this time 
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
Calendar cal = Calendar.getInstance();
// Set the parsed time to a Calendar object
cal.setTime(sdf.parse(stringDate));

現在，您必須獲取今天的日期，並使用Calendar#set方法設置上述時間。

// get today's time
Calendar today = Calendar.getInstance();
// print today date with current time,
System.out.println("Date before time is set: " + today.getTime());

// set today's hour to above time
today.set(Calendar.HOUR, cal.get(Calendar.HOUR));
// set today's minute to above time
today.set(Calendar.MINUTE, cal.get(Calendar.MINUTE));
// set today's seconds to above time
today.set(Calendar.SECOND, cal.get(Calendar.SECOND));
// print your new time
System.out.println("Date after time is set: " + today.getTime());

輸出：

Date before time is set: Thu Feb 05 02:52:55 PKT 2015
Date after time is set: Thu Feb 05 04:10:13 PKT 2015

您還可以將時間設置為一行，

today.set(today.get(Calendar.YEAR), today.get(Calendar.MONTH) , today.get(Calendar.DATE), cal.get(Calendar.HOUR), cal.get(Calendar.MINUTE), cal.get(Calendar.SECOND));

Answer 2

使用JodaTime

從當前時間建立一個DateTime

DateTime dt = new DateTime()
            .withMillisOfSecond(0)
            .withHourOfDay(21)
            .withMinuteOfHour(20)
            .withSecondOfMinute(0);

從模式構建DateTime

DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern(<YOUR_PATTERN>);
DateTime dt2 = dateTimeFormatter.parseDateTime(<YOUR_DATE_IN_A_STRING>);

比較日期時間

if(dt.isAfter(dt2)){
    // DO ANYTHING
} else if(dt.isBefore(dt2){
    // DO WHATEVER
}

從DateTime獲取日期

Date date = dt.toDate()

Answer 3

LocalDateTime（ http://www.journaldev.com/2800/java-8-date-time-api-example-tutorial-localdate-instant-localdatetime-parse-and-format ）在這里幫助了我：

import java.text.ParseException;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;

public class Test {

    public static void main(String[] args) throws ParseException {
        String time = "14:12:01";
        String[] timePieces= time.split(":");
        int H = Integer.parseInt(timePieces[0]);
        int m = Integer.parseInt(timePieces[1]);
        int s = Integer.parseInt(timePieces[2]);

        LocalDateTime today = LocalDateTime.of(LocalDate.now(), LocalTime.of(H, m, s));
        System.out.println(today);

        LocalDateTime today2 = LocalDateTime.now().withHour(H).withMinute(m).withSecond(s).withNano(0);
        System.out.println(today2);
    }

}

要將其轉換為“ Date”對象：

Date date = Date.from(today.atZone(ZoneId.systemDefault()).toInstant());