Java过滤器用户输入问题

Question

我正在尝试制作战舰。在这里，我想使用 Scanner 从控制台获取输入来确定拍摄地点。

while (x) {
    while (counter) {
        userInput = input.nextLine();
        if (userInput.equals("cheat")) {
            cheat = true;
        }

        uppercased = userInput.toUpperCase();
        char[] c = uppercased.toCharArray();

        if (uppercased.length() < 2) {
            System.out.println("Error, invalid input9, try again");
            break;
        } else if (uppercased.equals("")) {
            System.out.println("Error, invalid input1, try again");
            break;
        } else if (uppercased.length() > 2) {
            System.out.println("Error, invalid input2, try again");
            break;
        } else if (c[0] < 65 || c[0] > 74) {
            System.out.println("Error, invalid input3, try again");
            break;
        } else if (c[1] < 48 || c[1] > 57) {
            System.out.println("Error, invalid input4, try again");
            break;
        } else {
            code = uppercased;
            target = map.get(uppercased);
            targetPosition = target.getSymbol();
            if (targetPosition != 46) {
                System.out.println("You have shot here, try again");
                break;
            }
        }
        counter = false;

    }
    x = false;
    code = uppercased;
}

问题是，当我给出错误的输入时，它不会询问新的输入，但它会执行我的程序的其余部分。

它应该过滤输入，所以它是这样的: “A1” 而不是用来确定拍摄地点。 如何过滤错误的输入并获取新的输入？

Answer 1

• 使用 break 会将您移出当前循环。

• 使用继续，会将您移至当前循环的开头。

因此，在您的情况下，继续会更好，因为它会将您移至在内循环中读取输入的代码部分。

从这个循环中提取主体(如下所示)也很容易测试:)

更新:

while (x) {
    while (!runCheck()) { Your main method is extracted from loop, making it more readable
    }
    x = false;
    code = uppercased;
}

boolean runCheck(){
        userInput = input.nextLine();
        if ("cheat".equals(userInput)) { // prefer to compare String agains a constant in this way, it's immune to NPE, when by any chance userInput would be a null
            cheat = true;
        }

        uppercased = userInput.toUpperCase();
        char[] c = uppercased.toCharArray();

        if (uppercased.length() < 2) {
            System.out.println("Error, invalid input9, try again");
            return true;
        } else if ("".equals(uppercased)) {
        ...
        } else {
            code = uppercased;
            if(!map.conainsKey(uppercased)){ // target can be null, or not existing in map
               return true;
            }
            target = map.get(uppercased);
            targetPosition = target.getSymbol();
            if (targetPosition != 46) {
                System.out.println("You have shot here, try again");
                return true;
            }
        }
        return false;
}