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# 算法练习(24):日期类设计(1.2.11-1.2.12)

• 日期类的设计
• 异常处理
• 蔡勒公式

### 题目

1.2.11 根据Date的API实现一个SmartDate类型，在日期非法时抛出一个异常。

1.2.11 Develop an implementation SmartDate of our Date API that raises an excep- tion if the date is not legal.

### 答案

``````public class SmartDate {

@SuppressWarnings("unused")
private final int year;
@SuppressWarnings("unused")
private final int month;
@SuppressWarnings("unused")
private final int day;

public SmartDate(int year,int month,int day) throws Exception {
if (year < 0 || month < 0 || day < 0) {
Exception exception = new Exception("年月日要大于0");
throw exception;
}
if (month > 12) {
Exception exception = new Exception("年份要小于等于12");
throw exception;
}

switch (month) {
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
case 1:{
if (day > 31) {
Exception exception = new Exception(month + "月小于31号");
throw exception;
}
}
break;
case 2:{
if (day > 29) {
Exception exception = new Exception(month + "月小于31号");
throw exception;
}

int leapYear = year % 4;
if (leapYear != 0) {
if (day > 28) {
Exception exception = new Exception(month + "月小于29号");
throw exception;
}
}

}
break;
case 4:
case 6:
case 9:
case 11:{
if (day > 30) {
Exception exception = new Exception(month + "月小于30号");
throw exception;
}
}
break;

default:
break;
}

this.day    = day;
this.year   = year;
this.month  = month;
}

public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
SmartDate date = new SmartDate(2007, 1, 50);
}

}
``````

SmartDate1.java

### 题目

1.2.12 为SmartDate添加一个方法dayOfTheWeek()，为日期中每周的日返回Monday、Tuesday、Wednesday、Thursday……假定是21世纪

1.2.12 Add a method dayOfTheWeek() to SmartDate that returns a String value Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday, giving the ap- propriate day of the week for the date. You may assume that the date is in the 21st century.

### 答案

``````public class SmartDate2 {

@SuppressWarnings("unused")
private final int year;
@SuppressWarnings("unused")
private final int month;
@SuppressWarnings("unused")
private final int day;

private static final int YEARFIRSTTWO = 20;
private static final int DAYPERWEEK = 7;

public SmartDate2(int year, int month, int day) throws Exception {
if (year < 0 || month < 0 || day < 0) {
Exception exception = new Exception("年月日要大于0");
throw exception;
}
if (month > 12) {
Exception exception = new Exception("年份要小于等于12");
throw exception;
}

switch (month) {
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
case 1: {
if (day > 31) {
Exception exception = new Exception(month + "月小于31号");
throw exception;
}
}
break;
case 2: {
if (day > 29) {
Exception exception = new Exception(month + "月小于31号");
throw exception;
}

int leapYear = year % 4;
if (leapYear != 0) {
if (day > 28) {
Exception exception = new Exception(month + "月小于29号");
throw exception;
}
}

}
break;
case 4:
case 6:
case 9:
case 11: {
if (day > 30) {
Exception exception = new Exception(month + "月小于30号");
throw exception;
}
}
break;

default:
break;
}

this.day = day;
this.year = year;
this.month = month;
}

public String dayOfTheWeek(){
String resultWeek = "";
int tempMonth = this.month;
int tempYear = this.year;
int tempDay = this.day;
if (this.month == 1 || this.month == 2) {
tempMonth += 12;
tempYear --;
}

int y = tempYear - YEARFIRSTTWO * 100;
int floor1 = (int) Math.floor(y/4);
int floor2 = (int) (YEARFIRSTTWO / 4);
int floor3 = (int) Math.floor(26 * (tempMonth+1)/10);

int w = y + floor1 + floor2 -2 * YEARFIRSTTWO + floor3 + tempDay - 1;
int key = w % DAYPERWEEK;

if (key <0) {
key = key + 7;
}

switch (key) {
case 0:
resultWeek = "星期日";
break;
case 1:
resultWeek = "星期一";
break;
case 2:
resultWeek = "星期二";
break;
case 3:
resultWeek = "星期三";
break;
case 4:
resultWeek = "星期四";
break;
case 5:
resultWeek = "星期五";
break;
case 6:
resultWeek = "星期六";
break;

default:
break;
}

return resultWeek;
}

public String toString(){

return ""+ month + "/" + day + "/" + year;
}

public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
SmartDate2 date = new SmartDate2(2012, 2, 28);
String week = date.dayOfTheWeek();
System.out.println( date + " is :" + week);
}

}
``````

SmartDate2.java