我必须以 DDMMYYYY 格式拆分用户输入的日期。但是，如果您输入 70702000，它会显示我的所有 3 个错误，而不是一个
I have to split a date inputted by a user in the format DDMMYYYY. however if you input 70702000 its displaying all 3 of my errors instead of one
代码下方：
{
System.out.println("Please enter the date you would like to split");
System.out.println("Please make sure it is in the format DDMMYYYY");
date = sc.nextInt();
day = date / 1000000;
month = (date / 10000) - (day * 100);
year = date - (date / 10000) * (10000);
switch(day)
{
case 1: case 21: case 31:
suffix = "st";
break;
case 2: case 22:
suffix = "nd";
break;
case 3: case 23:
suffix = "rd";
break;
case 4: case 5: case 6: case 7: case 8: case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: case 19: case 20: case 24: case 25: case 26: case 27: case 28: case 29: case 30:
suffix = "th";
break;
default:
System.out.println("Error, Please enter a valid day (i.e. DD) that is between 01 - 31");
break;
}
switch(month)
{
case 4: case 6: case 9: case 11:
if ((day < 1) || (day > 30))
{
System.out.println("Error this day does not exist");
}
break;
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
if ((day < 1) || (day > 31))
{
System.out.println("Error this day does not exist");
}
break;
case 2:
if ((day < 1) || (day > 28))
{
if ((day != 29))
{
System.out.println("Error this day does not exist");
}
else if ((year % 4 != 0) || ((year % 400 != 0) && (year % 100 == 0)))
{
System.out.println("Error this day does not exist");
}
//If it isn't a leap year, febuary cannot have 29 days
}
break;
default:
System.out.println("Error this day does not exist");
}
switch(month)
{
case 1:
monthName = "January";
break;
case 2:
monthName = "Febuary";
break;
case 3:
monthName = "March";
break;
case 4:
monthName = "April";
break;
case 5:
monthName = "May";
break;
case 6:
monthName = "June";
break;
case 7:
monthName = "July";
break;
case 8:
monthName = "August";
break;
case 9:
monthName = "September";
break;
case 10:
monthName = "October";
break;
case 11:
monthName = "November";
break;
case 12:
monthName = "December";
default:
System.out.println("Error, Please make sure the month (i.e. MM) is between 01 and 12");
break;
}
if ((day == 29) && (month == 2))
{
System.out.println("It is the 29th day of Febuary in " + year + ".");
}
else
{
System.out.println("It is the " + day + suffix + " day of " + monthName + " in " + year + ".");
}
}
所以，基本上当我 运行 这个程序，并输入 70702020 值时，我会得到以下所有输出：
Error, Please enter a valid day (i.e. DD) that is between 01 - 31
Error this day does not exist
Error, Please make sure the month (i.e. MM) is between 01 and 12
然后它将输出最终输出（这仅在用户输入有效日期时才有用）
建议先看评论，再自己执行代码。
我添加一些评论。
public class TestFormatDate{
public static void main(String []args){
System.out.println("Please enter the date you would like to split");
System.out.println("Please make sure it is in the format DDMMYYYY");
//your input:70702020
int date = 70702020;
//70
int day = date / 1000000;
//70
int month = (date / 10000) - (day * 100);
//2020
int year = date - (date / 10000) * (10000);
String suffix = null;
String monthName = null;
switch(day)
{
case 1: case 21: case 31:
suffix = "st";
break;
case 2: case 22:
suffix = "nd";
break;
case 3: case 23:
suffix = "rd";
break;
case 4: case 5: case 6: case 7: case 8: case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: case 19: case 20: case 24: case 25: case 26: case 27: case 28: case 29: case 30:
suffix = "th";
break;
// day is 70, so the default is executed.
default:
System.out.println("Error, Please enter a valid day (i.e. DD) that is between 01 - 31");
break;
}
switch(month)
{
case 4: case 6: case 9: case 11:
if ((day < 1) || (day > 30))
{
System.out.println("Error this day does not exist");
}
break;
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
if ((day < 1) || (day > 31))
{
System.out.println("Error this day does not exist");
}
break;
case 2:
if ((day < 1) || (day > 28))
{
if ((day != 29))
{
System.out.println("Error this day does not exist");
}
else if ((year % 4 != 0) || ((year % 400 != 0) && (year % 100 == 0)))
{
System.out.println("Error this day does not exist");
}
//If it isn't a leap year, febuary cannot have 29 days
}
break;
// month is 70, so the default is executed.
default:
System.out.println("Error this day does not exist");
}
switch(month)
{
case 1:
monthName = "January";
break;
case 2:
monthName = "Febuary";
break;
case 3:
monthName = "March";
break;
case 4:
monthName = "April";
break;
case 5:
monthName = "May";
break;
case 6:
monthName = "June";
break;
case 7:
monthName = "July";
break;
case 8:
monthName = "August";
break;
case 9:
monthName = "September";
break;
case 10:
monthName = "October";
break;
case 11:
monthName = "November";
break;
case 12:
monthName = "December";
// month is 70, so the default is executed.
default:
System.out.println("Error, Please make sure the month (i.e. MM) is between 01 and 12");
break;
}
if ((day == 29) && (month == 2))
{
System.out.println("It is the 29th day of Febuary in " + year + ".");
}
// day is 70, so the else is executed.
else
{
System.out.println("It is the " + day + suffix + " day of " + monthName + " in " + year + ".");
}
}
}
您正在使用 switch 而不是 if(blah blah) 语句。意思是，该陈述是真实的并且现在产生错误。您的代码表明您的输入没有任何问题。您的后缀仍会打印，但会打印空引号，因为我相信它是一个空字符串。我建议在使用开关之前检查入口。或者使用 "System.exit(1)" 如果输入不正确，系统将退出。
编辑：根据计算，您的一天也将等于“70”，因此会出现其他错误。
break 仅跳出 switch 语句
您的 switch 语句中的 break 命令仅从 switch 语句中退出，不是您的整个方法。
您有一系列的三个 switch 语句。
- 当您跳出第一个 switch 语句时，控制流将转到第二个 switch 语句。
- 当您跳出第二个 switch 语句时，控制流转到第三个 switch 语句。
- 当您跳出第三个 switch 语句时，控制流将移至其余语句。
编程的核心概念之一是scope. You must learn to think in terms of boxes nested within boxes, like the Russian nesting dolls。在 switch 语句中，break 命令的作用域只是一条语句，而不是整个方法。 switch 语句是嵌套在外部方法中的一层作用域。 switch语句中的break只能"see"其直接包含框：switch语句。
java.time
顺便说一句，通过现代 java.time 类 解析为文本 简单得多。
try {
LocalDate ld =
LocalDate
.parse(
"70702020" ,
DateTimeFormatter.ofPattern( "ddMMuuuu" )
)
;
} catch ( DateTimeParseException e ) {
…
}
无效输入抛出 DateTimeParseException。
代码下方：
{
System.out.println("Please enter the date you would like to split");
System.out.println("Please make sure it is in the format DDMMYYYY");
date = sc.nextInt();
day = date / 1000000;
month = (date / 10000) - (day * 100);
year = date - (date / 10000) * (10000);
switch(day)
{
case 1: case 21: case 31:
suffix = "st";
break;
case 2: case 22:
suffix = "nd";
break;
case 3: case 23:
suffix = "rd";
break;
case 4: case 5: case 6: case 7: case 8: case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: case 19: case 20: case 24: case 25: case 26: case 27: case 28: case 29: case 30:
suffix = "th";
break;
default:
System.out.println("Error, Please enter a valid day (i.e. DD) that is between 01 - 31");
break;
}
switch(month)
{
case 4: case 6: case 9: case 11:
if ((day < 1) || (day > 30))
{
System.out.println("Error this day does not exist");
}
break;
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
if ((day < 1) || (day > 31))
{
System.out.println("Error this day does not exist");
}
break;
case 2:
if ((day < 1) || (day > 28))
{
if ((day != 29))
{
System.out.println("Error this day does not exist");
}
else if ((year % 4 != 0) || ((year % 400 != 0) && (year % 100 == 0)))
{
System.out.println("Error this day does not exist");
}
//If it isn't a leap year, febuary cannot have 29 days
}
break;
default:
System.out.println("Error this day does not exist");
}
switch(month)
{
case 1:
monthName = "January";
break;
case 2:
monthName = "Febuary";
break;
case 3:
monthName = "March";
break;
case 4:
monthName = "April";
break;
case 5:
monthName = "May";
break;
case 6:
monthName = "June";
break;
case 7:
monthName = "July";
break;
case 8:
monthName = "August";
break;
case 9:
monthName = "September";
break;
case 10:
monthName = "October";
break;
case 11:
monthName = "November";
break;
case 12:
monthName = "December";
default:
System.out.println("Error, Please make sure the month (i.e. MM) is between 01 and 12");
break;
}
if ((day == 29) && (month == 2))
{
System.out.println("It is the 29th day of Febuary in " + year + ".");
}
else
{
System.out.println("It is the " + day + suffix + " day of " + monthName + " in " + year + ".");
}
}
所以，基本上当我 运行 这个程序，并输入 70702020 值时，我会得到以下所有输出：
Error, Please enter a valid day (i.e. DD) that is between 01 - 31
Error this day does not exist
Error, Please make sure the month (i.e. MM) is between 01 and 12
然后它将输出最终输出（这仅在用户输入有效日期时才有用）
建议先看评论，再自己执行代码。 我添加一些评论。
public class TestFormatDate{
public static void main(String []args){
System.out.println("Please enter the date you would like to split");
System.out.println("Please make sure it is in the format DDMMYYYY");
//your input:70702020
int date = 70702020;
//70
int day = date / 1000000;
//70
int month = (date / 10000) - (day * 100);
//2020
int year = date - (date / 10000) * (10000);
String suffix = null;
String monthName = null;
switch(day)
{
case 1: case 21: case 31:
suffix = "st";
break;
case 2: case 22:
suffix = "nd";
break;
case 3: case 23:
suffix = "rd";
break;
case 4: case 5: case 6: case 7: case 8: case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: case 19: case 20: case 24: case 25: case 26: case 27: case 28: case 29: case 30:
suffix = "th";
break;
// day is 70, so the default is executed.
default:
System.out.println("Error, Please enter a valid day (i.e. DD) that is between 01 - 31");
break;
}
switch(month)
{
case 4: case 6: case 9: case 11:
if ((day < 1) || (day > 30))
{
System.out.println("Error this day does not exist");
}
break;
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
if ((day < 1) || (day > 31))
{
System.out.println("Error this day does not exist");
}
break;
case 2:
if ((day < 1) || (day > 28))
{
if ((day != 29))
{
System.out.println("Error this day does not exist");
}
else if ((year % 4 != 0) || ((year % 400 != 0) && (year % 100 == 0)))
{
System.out.println("Error this day does not exist");
}
//If it isn't a leap year, febuary cannot have 29 days
}
break;
// month is 70, so the default is executed.
default:
System.out.println("Error this day does not exist");
}
switch(month)
{
case 1:
monthName = "January";
break;
case 2:
monthName = "Febuary";
break;
case 3:
monthName = "March";
break;
case 4:
monthName = "April";
break;
case 5:
monthName = "May";
break;
case 6:
monthName = "June";
break;
case 7:
monthName = "July";
break;
case 8:
monthName = "August";
break;
case 9:
monthName = "September";
break;
case 10:
monthName = "October";
break;
case 11:
monthName = "November";
break;
case 12:
monthName = "December";
// month is 70, so the default is executed.
default:
System.out.println("Error, Please make sure the month (i.e. MM) is between 01 and 12");
break;
}
if ((day == 29) && (month == 2))
{
System.out.println("It is the 29th day of Febuary in " + year + ".");
}
// day is 70, so the else is executed.
else
{
System.out.println("It is the " + day + suffix + " day of " + monthName + " in " + year + ".");
}
}
}
您正在使用 switch 而不是 if(blah blah) 语句。意思是，该陈述是真实的并且现在产生错误。您的代码表明您的输入没有任何问题。您的后缀仍会打印，但会打印空引号，因为我相信它是一个空字符串。我建议在使用开关之前检查入口。或者使用 "System.exit(1)" 如果输入不正确，系统将退出。
编辑：根据计算，您的一天也将等于“70”，因此会出现其他错误。
break 仅跳出 switch 语句
您的 switch 语句中的 break 命令仅从 switch 语句中退出，不是您的整个方法。
您有一系列的三个 switch 语句。
- 当您跳出第一个 switch 语句时，控制流将转到第二个 switch 语句。
- 当您跳出第二个 switch 语句时，控制流转到第三个 switch 语句。
- 当您跳出第三个 switch 语句时，控制流将移至其余语句。
编程的核心概念之一是scope. You must learn to think in terms of boxes nested within boxes, like the Russian nesting dolls。在 switch 语句中，break 命令的作用域只是一条语句，而不是整个方法。 switch 语句是嵌套在外部方法中的一层作用域。 switch语句中的break只能"see"其直接包含框：switch语句。
java.time
顺便说一句，通过现代 java.time 类 解析为文本 简单得多。
try {
LocalDate ld =
LocalDate
.parse(
"70702020" ,
DateTimeFormatter.ofPattern( "ddMMuuuu" )
)
;
} catch ( DateTimeParseException e ) {
…
}
无效输入抛出 DateTimeParseException。