java - 作业: Why is catch being bypassed?

Question

我有以下代码:

public static String userInput(Scanner input) {
    String date = "";
    int year = 0;
    try{
        System.out.print("Please enter a date (mm/dd/yyyy): ");
        date = input.next();            
        boolean leapYear = getLeapYear(date);               
        boolean dateCheck = checkDate(date,leapYear);
        if(dateCheck == true) {
            return date;
        }           
    } catch(IllegalArgumentException e) {
        System.out.println(year + " " + "is not a leap year");

    }
    return date;                
}   

我已通过调试验证，当我输入非闰年日期(例如 02/29/1601)时，dateCheck 为 false。我认为会发生的是，当 if 语句为 false 时，程序将继续捕获。相反，它完全跳过捕获并转到返回日期。我哪里出错了？

Answer 1

Catch 仅在 try 主体抛出 Exception 时运行(在您的示例中仅抛出 IllegalArgumentException)。如果您希望代码始终运行，则应将其放在 finally block 中。 -

try{
    System.out.print("Please enter a date (mm/dd/yyyy): ");
    date = input.next();            
    boolean leapYear = getLeapYear(date);               
    boolean dateCheck = checkDate(date,leapYear);
    if(dateCheck == true) {
        return date;
    } else {
        // what you seem to have expected.
        throw new IllegalArgumentException("not a leap year");
    }        
} catch(IllegalArgumentException e) {
    System.out.println(year + " " + "is not a leap year");
} finally {
    System.out.println("This will always print.").
}
return null;