java第一个dowhile循环运行不正常

Question

我的代码似乎有问题。我的代码检测非整数，并不断要求用户输入正#，但当您插入负#时，它只要求用户输入一次正。怎么了？我的do while循环肯定有问题。 我只关注第一个，然后我可以做第二个

import java.util.Scanner;

public class scratch {

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);

    int firstN = 0;
    int secondN = 0;
    boolean isNumber = false;
    boolean isNumPos = false;

    System.out.print("Enter a positive integer: ");

    do {
        if (input.hasNextInt()) {
            firstN = input.nextInt();
            isNumber = true;
        }
        if (firstN > 0) {
            isNumPos = true;
            isNumber = true;
            break;
        } else { 
            isNumPos = false;
            isNumber = false;
            System.out.print("Please enter a positive integer: ");
            input.next();
            continue;

        }

    } while (!(isNumber) || !(isNumPos));

    System.out.print("Enter another positive integer: ");
    do {
        if (input.hasNextInt()) {
            secondN = input.nextInt();
            isNumber = true;
        }
        if (secondN > 0) {
            isNumPos = true;
            isNumber = true;
        } else {
            isNumPos = false;
            isNumber = false;
            System.out.print("Please enter a positive integer: ");
            input.next();
        }

    } while (!(isNumber) || !(isNumPos));

    System.out.println("The GCD of " + firstN + " and " + secondN + " is " + gCd(firstN, secondN));

}

public static int gCd(int firstN, int secondN) {
    if (secondN == 0) {
        return firstN;
    } else
        return gCd(secondN, firstN % secondN);
}

}

Answer 1

试试这段代码

while (true){
  System.out.println("Please enter Positive number");
  boolean hasNextInt = scanner.hasNextInt();
  if(hasNextInt){
    int firstNum = scanner.nextInt();
    if(firstNum>0){
      break;
    }else{
      continue;
    }
  }else{
    scanner.next();
    continue;
  }
}

Answer 2

在这种情况下，您需要读取两次输入：

        firstN = input.nextInt();
        ...
        input.next ();

添加一些指示变量或重新组织代码，以便在通过第一次读取进行读取时，避免使用第二次读取