爪哇時間執行

Question

package timeToys; 

import java.util.regex.Pattern; 


** 
* A DayTime is an immutable object that stores a moment of day represented in 
* hour, minutes and seconds. Day or year are not defined. 
* 
* @author marius.costa <marius.costa@yahoo.com> 
*/ 

public class DayTime {`enter code here` 

    private int hour;// hour of the day 
    private int minute;// minute of the hour 
    private int second;// second of the minute 
    private String time;// time as string 

    private static final String TIME_LONG_FORMAT = "([01]?[0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9]"; 
    private static final String TIME_SHORT_FORMAT = "([01]?[0-9]|2[0-3]):[0-5][0-9]"; 

    /** 
    * Class private constructor that creates new objects using inner builder. 
    * 
    * @param timeBuilder - builder for new DayTime objects defined as inner class. 
    */ 
    private DayTime(Builder timeBuilder) { 
     this.hour = timeBuilder.hour; 
     this.minute = timeBuilder.minute; 
     this.second = timeBuilder.second; 
     this.time = timeBuilder. time; 
    } 

    public int getHour() { 
     return hour; 
    } 

    public int getMinute() { 
     return minute; 
    } 

    public int getSecond() { 
     return second; 
    } 

    @Override 
    public String toString() { 
     return time; 
    } 

    /** 
    * Builder is a inner class that creates new DayTime objects based on int params 
    * (hour, minute, second), or by parsing a String param formated as 
    * 'HH:mm' or 'HH:mm:ss'. 
    */ 
    public static class Builder { 
     private int hour = 0; 
     private int minute = 0; 
     private int second = 0; 
     private String time; 

     /** 
     * Constructor that creates a Builder from a String param formated as 
     * 'HH:mm' or 'HH:mm:ss'. 
     * @param time - must be formated as 'HH:mm' or 'HH:mm:ss'. 
     */ 
     public Builder(String time) { 
      this.time = time; 
     } 

     /** 
     * Creates a DayTime object from the String {@link #time}. 
     * The String {@code time} is innitialy parsed to validate time 
     * in 24 hours format with regular expression. 
     * If not, RuntimeExceptions will be thrown. 
     * 
     * 
     * @return DayTime 
     * @throws IllegalArgumentException if the string isn't right formated. 
     * @throws NumberFormatException if int values cannot be extracted from String time. 
     */ 
     public DayTime createTime() { 
      String[] timeUnits = time.split(":"); 
      if(Pattern.compile(TIME_SHORT_FORMAT).matcher(time).matches()) { 
       this.hour = Integer.parseInt(timeUnits[0]); 
       this.minute = Integer.parseInt(timeUnits[1]); 
      } else if(Pattern.compile(TIME_LONG_FORMAT).matcher(time).matches()) { 
       this.hour = Integer.parseInt(timeUnits[0]); 
       this.minute = Integer.parseInt(timeUnits[1]); 
       this.second = Integer.parseInt(timeUnits[2]); 
      } else { 
       throw new IllegalArgumentException("Invalid time format" + 
       " (Expected format: 'HH:mm' or 'HH:mm:ss')."); 
      } 
      return new DayTime(this); 
     } 
    } 
} 

Answer 1

您可以考慮添加方法：

equals()

hash()

，並實現Comparable接口

int compareTo(Object other)

而且，推薦，使其不可變的。

例如，如果你使用這個類來檢查，如果事情已經發生：

class Remainder { 
    private String what; 
    private DateTime when; 


    public static Remainder remindMe(String what, DateTime when) { 
     Reminder r = new Reminder(); 
     r.what = what; 
     r.when = when; 
    } 

    public boolean isTimeAlready() { 
      //return DateTime.Builder.createTime().compareTo(this.when) > 0; 
      // implemented somehow 
      return isCurrentTimeGreaterThan(this.when); // assume it return true if current time is after "when" 
    } 
    } 

如果你使用這樣的：

DateTime atSix = new DateTime(18, 0, 0); 

    Reminder reminder = Reminder.remindMe("Go for the milk", atSix); 

和時針改變（按課程的錯誤）

atSix.setHour(1); 

這不會是任何使用的「提醒」對象，變量when是私人的，因爲它的引用被保留在外面，並且沒有對它的控制，因此它變得不可靠。

這將是一個非常奇怪的錯誤，你可能會介紹。使用不可變對象不太容易出錯。這就是爲什麼Java中的核心對象如String，Integer和其他許多其他類型是不可變的原因。

如果你可以讀這本書：Effective Java它將轉變180度你Java的觀點。

Answer 2

不這樣做。抵制所有誘惑寫你自己的日期/時間代碼。它會咬你

使用標準的日期類 - 甚至壽它似乎是一種浪費

Answer 3

使用JodaTime。

Answer 4

退房http://veyder-time.enblom.org - 一個功能強大且簡單的替代java.util中，喬達時間等