java - 捕获异常后如何在 for 循环中不增加？

Question

这是我的老师的提示:

Put the TRY block with the CATCH clause INSIDE THE FOR/WHILE LOOP so if the SPECIFIC exception is thrown from the constructor , you will display an error message, and NOT INCREMENT the counter.

这是我的构造函数和这部分的代码:

public CreditCardNumber(String id, String accNum) {
    this();
    if (id == null || accNum == null || id.length() != 6 || accNum.length() != 9 || 
        isDigit(id) == false || isDigit(accNum) == false) {

        throw new IllegalArgumentException("Either parameter is null or has incorrect length or doesn't have all digits");
    } else {
        accountNum = accNum;
        issuerId = id;

        setCheckDigit();
    }
}

///

for (int i = 0; i < arrLength; i++) {
    try { 
        System.out.println("Enter an issuer ID# (6 digits) for element #" + i);
        String issuerId = scanner.next();
        System.out.println("Enter an account # (9 digits) for element #" + i);
        String accountNum = scanner.next();
        CreditCardNumber obj = new CreditCardNumber(issuerId, accountNum);
        obj.changeId(issuerId);
    } catch (IllegalArgumentException e) {
        throw new IllegalArgumentException("Invalid Input, Try Again!")
        continue;
    }
}

现在我遇到的麻烦是如何实现此代码，以便在捕获异常后，代码重新提示用户输入捕获异常的相同 i 值的值。基本上如何做捕获异常后我不增加循环吗？我尝试继续；方法，编译器说代码无法访问。请帮忙!

Answer 1

不必在 for 循环的第三部分中使用一元 ++ 运算符递增 i ，只需在 try block 的末尾执行此操作即可:

for (int i = 0; i < arrLength;) { // removed here
    try { 
        System.out.println("Enter an issuer ID# (6 digits) for element #" + i);
        String issuerId = scanner.next();
        System.out.println("Enter an account # (9 digits) for element #" + i);
        String accountNum = scanner.next();
        CreditCardNumber obj = new CreditCardNumber(issuerId, accountNum);
        obj.changeId(issuerId);
        i++; // added here
    } catch (IllegalArgumentException e) {
        System.out.println("Invalid Input, Try Again!"); // don't throw just print
    }
}

此外，我建议以

的形式替换构造函数中的 boolean 检查

if(variable == false){...}

仅

if(!variable){...}