如何检查System.In是否只包含数字

Question

有一个任务从控制台得到N个数字，找到最长和最短的一个和他们的长度。任务并不难，工作正常，但我决定做一个检查，如果控制台输入与任务的条件相对应：

• 只有整数。
• 是精确的N个数字，而不是更多/更少。

我决定编写一个布尔方法isinputCorret()，它将使用扫描器并检查输入是否正确，但它不能正常工作。

public static void main(String[] args) {
    int n = 5;
    Scanner sc = new Scanner(System.in);
    do {
        System.out.println("Hello, please enter " + n + " integer numbers:");
        while (!isInputCorrect(sc,n)){
            System.out.println("Wrong! Try again:");
            sc.next();
        }
    } while (!isInputCorrect(sc, 5));

    String scLine = sc.nextLine();
    String[] arr = scLine.split("\\s+");

    String maxLengthNum = arr[0];
    String minLengthNum = arr[0];
    for (int i = 1; i < arr.length; i++){
        if (maxLengthNum.length() < arr[i].length()){
            maxLengthNum = arr[i];
        }
        if (minLengthNum.length() > arr[i].length()){
            minLengthNum = arr[i];
        }
    }

    String equalMaxNum = "";
    String equalMinNum = "";

    int countMax = 0;
    int countMin = 0;

    for (String s : arr){
        if (maxLengthNum.length() == s.length()){
            countMax += 1;
            equalMaxNum += s + " ";
        }
        if (minLengthNum.length() == s.length()){
            countMin += 1;
            equalMinNum += s + " ";
        }
    }
    if (countMax > 1){
        System.out.println("The longest numbers are: " + equalMaxNum + " Their length is: " + maxLengthNum.length());
    }
    else {
        System.out.println("The longest number is: " + maxLengthNum + " Its length is: " + maxLengthNum.length());
    }
    if (countMin > 1){
        System.out.println("The shortest numbers are: " + equalMinNum + " Their length is: " + minLengthNum.length());
    }
    else {
        System.out.println("The shortest number is: " + minLengthNum + " Its length is: " + minLengthNum.length());
    }
}
public static boolean isInputCorrect(Scanner sc, int n){
    boolean flag = true;
    for (int i = 0; i < n; i++){
        if (sc.hasNextInt()){
            sc.next();
        }else {
            flag = false;
            break;
        }
    }
    return flag;
}

Answer 1

您可以使用正则表达式来验证输入是否仅包含整数：

int n = 5;
// ... your current code

String scLine = sc.nextLine();
if (!scLine.matches("\\d+(?:\\s+\\d+)*")) {
    throw new IllegalArgumentException("input contained non-integers");
}

String[] arr = scLine.split("\\s+");
if (arr.length != n) {
    throw new IllegalArgumentException("found " + arr.length + " number inputs but expected " + n + ".");
}