[英]Why doesn't my Do While loop stop after the condition is not met?
我编写了一个代码，它获取用户在开始日期和结束日期的输入，并检查它们是否有效。 在下面的代码中，我有 2 个 do..while 循环。 一个用于开始日期，另一个用于结束日期。 当执行第一个循环并且不满足条件时，程序不会继续执行另一个 do while 循环。 如果我能收到此问题的解决方案，那将很有帮助。
int year, startMonth, endMonth, startDay, endDay;
boolean checkStartDate = false, checkEndDate = false;
Scanner input = new Scanner (System.in);
//checking Start Date
do
{
checkStartDate = false;
System.out.print("Enter the year: ");
year = input.nextInt();
System.out.print("Enter the start month: ");
startMonth = input.nextInt();
System.out.print("Enter the start day: ");
startDay = input.nextInt();
switch (startMonth)
{
case 1:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 2:
if(startDay <= 28)
{
checkStartDate = true;
}
break;
case 3:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 4:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 5:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 6:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 7:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 8:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 9:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 10:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 11:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 12:
if(startDay <= 31)
{
checkStartDate = true;
return;
}
default:
checkStartDate = false;
System.out.println("Try again and enter a valid date \n");
}
checkStartDate = false;
} while (checkStartDate = true);
//checking End Date
do
{
checkEndDate = false;
System.out.print("Enter the year: ");
year = input.nextInt();
System.out.print("Enter the start month: ");
endMonth = input.nextInt();
System.out.print("Enter the start day: ");
endDay = input.nextInt();
switch (endMonth)
{
case 1:
if(endDay <= 31)
{
checkEndDate = true;
}
else
{
checkEndDate = false;
System.out.println("Print a valid start day");
}
break;
case 2:
if(endDay <= 28)
{
checkEndDate = true;
}
break;
case 3:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 4:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 5:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 6:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 7:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 8:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 9:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 10:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 11:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 12:
if(endDay <= 31)
{
checkEndDate = true;
return;
}
default:
checkEndDate = false;
System.out.println("Try again and enter a valid date \n");
}
checkEndDate = false;
} while (checkEndDate = true);
System.out.println("correct ");
while (checkEndDate = true)
您将checkEndDate指定为 true，因此循环将始终重复。 你可能的意思是：
while (checkEndDate == true)
这将比较两个值。 但既然你已经有了 boolean，你就不需要比较了：
while (checkEndDate)
请注意，您可以通过组合相似的案例来显着减少代码量。 例如：
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
30 天的月份也是如此。
您还应该编写一个checkDate()方法，这样您就不会重复编写相同的代码。
你添加了checkStartDate= false & checkEndDate = false; 每个 do while 循环结束。 这不是必需的。
将 while 条件更新为while (checkStartDate); 用 Boolean 值评估。
下面是工作代码
int 年，开始月，结束月，开始日，结束日； boolean checkStartDate = false，checkEndDate = false； 扫描仪输入 = 新扫描仪（System.in）；
//checking Start Date
do
{
checkStartDate = false;
System.out.print("Enter the year: ");
year = input.nextInt();
System.out.print("Enter the start month: ");
startMonth = input.nextInt();
System.out.print("Enter the start day: ");
startDay = input.nextInt();
switch (startMonth)
{
case 1:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 2:
if(startDay <= 28)
{
checkStartDate = true;
}
break;
case 3:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 4:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 5:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 6:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 7:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 8:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 9:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 10:
if(startDay <= 31)
{
checkStartDate = true;
}
break;
case 11:
if(startDay <= 30)
{
checkStartDate = true;
}
break;
case 12:
if(startDay <= 31)
{
checkStartDate = true;
return;
}
default:
checkStartDate = false;
System.out.println("Try again and enter a valid date \n");
}
// checkStartDate = false;
} while (checkStartDate);
//checking End Date
do
{
checkEndDate = false;
System.out.print("Check End Date... ");
System.out.print("Enter the year: ");
year = input.nextInt();
System.out.print("Enter the start month: ");
endMonth = input.nextInt();
System.out.print("Enter the start day: ");
endDay = input.nextInt();
switch (endMonth)
{
case 1:
if(endDay <= 31)
{
checkEndDate = true;
}
else
{
checkEndDate = false;
System.out.println("Print a valid start day");
}
break;
case 2:
if(endDay <= 28)
{
checkEndDate = true;
}
break;
case 3:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 4:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 5:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 6:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 7:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 8:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 9:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 10:
if(endDay <= 31)
{
checkEndDate = true;
}
break;
case 11:
if(endDay <= 30)
{
checkEndDate = true;
}
break;
case 12:
if(endDay <= 31)
{
checkEndDate = true;
return;
}
default:
checkEndDate = false;
System.out.println("Try again and enter a valid date \n");
}
// checkEndDate = false;
} while (checkEndDate);
System.out.println("correct ");
当满足while条件时，为什么第一次do while循环没有结束？
[英]Why doesn't the first do while loop end when the while condition is met?
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