Java的：我需要Date类帮助

Question

// Date3.java 
// Date3 class declaration. 

public class Date3 
{ 
    private int month; // 1-12 
    private int day; // 1-31 based on month 
    private int year; // any year 
    private String[] months = new String[]{ "january", "february", "march", "april", "may", "june", "july", "august", "september", "october", "november", "december" }; 


    // constructor: call checkMonth to confirm proper value for month; 
    // call checkDay to confirm proper value for day 
    public Date3(int theMonth, int theDay, int theYear) 
    { 
     month = checkMonth(theMonth); // validate month 
     year = theYear; // could validate year 
     day = checkDay(theDay); // validate day 

     System.out.printf( 
     "Date3 object constructor for date %s\n", this); 
    } // end Date3 constructor 

    public Date3(String m, int d, int y){ 
     this(m, d, y); 
    } 

    public Date3(int m, int y){ 
     this(m,0, y); 
    } 


    // utility method to confirm proper month value 
    private int checkMonth(int testMonth) 
    { 
     if (testMonth > 0 && testMonth <= 12) // validate month 
     return testMonth; 
     else // month is invalid 
     { 
     System.out.printf( 
      "Invalid month (%d) set to 1.", testMonth); 
     return 1; // maintain object in consistent state 
     } // end else 
    } // end method checkMonth 

    // utility method to confirm proper day value based on month and year 
    private int checkDay(int testDay) 
    { 
     int[] daysPerMonth = 
     { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; 

     // check if day in range for month 
     if (testDay > 0 && testDay <= daysPerMonth[ month ]) 
     return testDay; 

     // check for leap year 
     if (month == 2 && testDay == 29 && (year % 400 == 0 || 
      (year % 4 == 0 && year % 100 != 0))) 
     return testDay; 

     System.out.printf("Invalid day (%d) set to 1.", testDay); 
     return 1; // maintain object in consistent state 
    } // end method checkDay 

    public String getMonthString(int month){ 
     return months[month]; 
     } 


    /* public String monthAsString() 
    { 
     //returns month as a string rather than an integer 
     switch (month) 
     { 
      case 1: return "January"; 
      case 2: return "February"; 
      case 3: return "March"; 
      case 4: return "April"; 
      case 5: return "May"; 
      case 6: return "June"; 
      case 7: return "July"; 
      case 8: return "August"; 
      case 9: return "September"; 
      case 10: return "October"; 
      case 11: return "November"; 
      case 12: return "December"; 
      default: return "";   
     }   
    }*/ 




    // return a String of the form month/day/year 
    public String toString() 
    { 
     return String.format("%d/%d/%d", month, day, year); 
    } // end method toString 
} // end class Date3 





public class Date3Test { 

    /** 
    * @param args 
    */ 
    public static void main(String[] args) { 
     // TODO Auto-generated method stub 

     Date3 myDate = new Date3(9, 16, 2011); 
     Date3 myDate2 = new Date3("June", 24, 2010); 
     Date3 myDate3 = new Date3(259, 2005); 

     // all three dates above are equal and will therefore print 
     // the same dates 

     System.out.println(myDate); 
     System.out.println(myDate2); 
     System.out.println(myDate3); 

    } 

} 

Answer 1

我能理解为什么你提供的模板可能对于初学者是有问题的：一方面，几个月阵也不是一成不变的，在另一方面你超载构造函数在它们必须委托给this（int，int，int） - 构造函数之前无法访问它。

要修复代码，您必须声明月份数组静态，请创建一个将您的月份字符串转换为月份数的静态方法。此外，你必须注释掉特定的行甚至编译和测试这个。

因此，让我们解决（II）一起

替换：

private String[] months 

有：

private static String[] months 

替换：

public Date3(String m, int d, int y){ 
    this(m, d, y); 
} 

有：

public Date3(String m, int d, int y){ 
    this(convMonth(m), d, y); 
} 
public static int convMonth(String m) { 
    int index =1; // january will be 1 
    for(String month : months) { 
     if(m.equals(month)) break; 
     index++; 
    } 
    return index; 
} 

注释掉第二个构造模板，像这样：

/*public Date3(int m, int y){ 
    this(m,0, y); 
}*/ 

而且注释掉在Date3Test.java调用到第二个构造模板：

//System.out.println(myDate3); 

现在这应该编译并运行，并为你提供（ii）的帮助。你可以自己解决（iii），只需实现注释掉的第二个构造函数模板并重新激活println（）。

Answer 2

好吧，关于（III）：

我认为你不能使用java Date类，所以你必须这样做：以DDD转换为月份和日期的日，你将有首先定义该年份的月份日期阵列，这当然取决于当年的2月份是28天还是29天。在正常情况下它是这样的：

INT [] monthDays =新INT [12] {31,28,31,30,31,30,31,31,30,31,30,31}

年被4整除的情况下，除了那些100，除由400（参见维基百科为闰年），你将不得不改变28至29

好吧，你DDD你转换可以这样做：遍历该数组，直到您的DDD小于当前单元格中存储的值，然后减去当前单元格，并记住您向前移动了一个月。例如：DDD = 41 - >减去31 - >日期是2月10日。