Read Sean

好了，來看我在Common Lang中最后要講的一個包：org.apache.commons.lang.time。這個包里面包含了如下5個類：

DateFormatUtils – 提供格式化日期和時間的功能及相關常量；

DateUtils – 在Calendar和Date的基礎上提供更方便的訪問；

DurationFormatUtils – 提供格式化時間跨度的功能及相關常量；

FastDateFormat – 為java.text.SimpleDateFormat提供一個的線程安全的替代類；

StopWatch – 是一個方便的計時器。

我們還是在一個例子中來看上述各個類的用法吧：

package sean.study.jakarta.commons.lang;

import java.util.Calendar;

import java.util.Date;

import org.apache.commons.lang.StringUtils;

import org.apache.commons.lang.time.DateFormatUtils;

import org.apache.commons.lang.time.DateUtils;

import org.apache.commons.lang.time.FastDateFormat;

import org.apache.commons.lang.time.StopWatch;

public class DateTimeUsage {

    public static void main(String[] args) {

        demoDateUtils();

        demoStopWatch();

    }

    public static void demoDateUtils() {

        System.out.println(StringUtils.center(" demoDateUtils ", 30, "="));

        Date date = new Date();

        String isoDateTime = DateFormatUtils.ISO_DATETIME_FORMAT.format(date);

        String isoTime = DateFormatUtils.ISO_TIME_NO_T_FORMAT.format(date);

        FastDateFormat fdf = FastDateFormat.getInstance("yyyy-MM");

        String customDateTime = fdf.format(date);

        System.out.println("ISO_DATETIME_FORMAT: " + isoDateTime);

        System.out.println("ISO_TIME_NO_T_FORMAT: " + isoTime);

        System.out.println("Custom FastDateFormat: " + customDateTime);

        System.out.println("Default format: " + date);

        System.out.println("Round HOUR: " + DateUtils.round(date, Calendar.HOUR));

        System.out.println("Truncate HOUR: " + DateUtils.truncate(date, Calendar.HOUR));

        System.out.println();

    }

    public static void demoStopWatch() {

        System.out.println(StringUtils.center(" demoStopWatch ", 30, "="));

        StopWatch sw = new StopWatch();

        sw.start();

        operationA();

        sw.stop();

        System.out.println("operationA used " + sw.getTime() + " milliseconds.");

        System.out.println();

    }

    public static void operationA() {

        try {

            Thread.sleep(999);

        }

        catch (InterruptedException e) {

            // do nothing

        }

    }

}

以下是運行結果：

======= demoDateUtils ========

ISO_DATETIME_FORMAT: 2005-08-01T12:41:51

ISO_TIME_NO_T_FORMAT: 12:41:51

Custom FastDateFormat: 2005-08

Default format: Mon Aug 01 12:41:51 CST 2005

Round HOUR: Mon Aug 01 13:00:00 CST 2005

Truncate HOUR: Mon Aug 01 12:00:00 CST 2005

======= demoStopWatch ========

operationA used 1000 milliseconds.

具體的調用細節和完整的API請參閱Commons Lang的Javadoc。