Java 循环扫描仪输入直到输入或 "e" 没有 .split

Question


public class test {

   private static Scanner userpress = new Scanner(System.in);

   public static void main(String[] args) {
      int r = 0;
      int h = 0;

      System.out.println("---------------------------------");
      System.out.println("write your two numbers (numerator, denominator)");

      userpress.useDelimiter("\s"); // here
      while (userpress.hasNextInt()) {

         r = userpress.nextInt();
         h = userpress.nextInt();
         // userpress.nextLine(); // remove
         int x = r / h;
         System.out.print(x + " ");

      }

   }

   private static void message() {
      System.out.println("user pressed e");

   }

}

这个程序要求用户至少输入2个，第一个输入是分子，第二个是分母，然后它会给出numerator/denominator的值并打印出来。这是我想要做的：我希望能够写下尽可能多的数字，例如 10 5 20 4，输出应该是 2, 5 如果我写 10 5 20 4 30 5 输出应该是 2, 5, 6。然而，这只适用于偶数。如果我写的是奇数，例如 10 5 3，那么程序就会崩溃，因为 2 没有被除以任何东西。我希望程序在不均匀的情况下删除最后一个输入，例如，如果输入为 10 5 3，则输出应为 2，因为 10/5=2 并且应丢弃最后一个输入。我该如何解决这个问题？问题 2：例如，如果我在数字后面写一个 e； 10 5 20 4 e，那么我希望输出为2, 5 user pressed e 我不想使用 .split，我必须使用 hasnext... 和 next()

Answer 1

您可以使用正则表达式来检查 space，而不是只取 space 之前的第一部分。像这样：

  import java.util.Scanner;

  public class Main {

    private static Scanner userpress = new Scanner(System.in);

    public static void main(String[] args) {
        String first;
        String second;

        System.out.println("---------------------------------");
        System.out.println("write your two numbers (numerator, denominator)");

        userpress.useDelimiter("\s"); // here
        while (userpress.hasNextLine()) {

            first = userpress.nextLine();
            second = userpress.nextLine();
            if(first.contains(" ") || second.contains(" ")) {
                String[] firstParts = first.split(" ");
                String[] secondParts = second.split(" ");
                first = firstParts[0];
                second = secondParts[0];
            }
            // userpress.nextLine(); // remove
            int x = Integer.valueOf(first) / Integer.valueOf(second);
            System.out.print(x + " ");

        }

    }

    private static void message() {
        System.out.println("user pressed e");

    }

}

Answer 2

您的代码存在的问题是您通过一次检查 userpress.hasNextInt() 来扫描两个整数。每次扫描整数时都应该进行此检查。

工作代码：

import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        int r = 0;
        int h = 0;
        System.out.print("Write your two numbers (numerator, denominator): ");
        Scanner userpress = new Scanner(System.in);
        userpress.useDelimiter("\s");

        while (userpress.hasNextInt()) {
            r = userpress.nextInt();
            if (userpress.hasNextInt()) {
                h = userpress.nextInt();
                int x = r / h;
                System.out.print(x + " ");
            } else {
                break;
            }
        }
        String s = userpress.next();
        if ("e".equalsIgnoreCase(s)) {
            message();
        }
    }

    private static void message() {
        System.out.println("user pressed e");
    }
}

样本运行:

Write your two numbers (numerator, denominator): 10 5 3 e
2 user pressed e

另一个样本运行:

Write your two numbers (numerator, denominator): 10 5 3
2

另一个样本运行:

Write your two numbers (numerator, denominator): 10 5 20 5
2 4

另一个样本运行:

Write your two numbers (numerator, denominator): 10 5 20 5 e
2 4 user pressed e

Answer 3

或者，如果您不介意多使用一点 space，您可以想出一个简单的算法，例如：

public class Main {

    private static Scanner userpress = new Scanner(System.in);

    public static void main(String[] args) {
        System.out.println("---------------------------------");
        System.out.println("write your two numbers (numerator, denominator)");
        userpress.useDelimiter("\s");

        List<Integer> numbers = new ArrayList<>();

        while(userpress.hasNextInt()) {
            numbers.add(userpress.nextInt());
        }

        for (int i=0; i<numbers.size()-1; i+=2) {
            int x = numbers.get(i)/numbers.get(i+1);
            System.out.print(x + " ");
        }
    }
}

Java 循环扫描仪输入直到输入或 "e" 没有 .split

Java loop scanner input until enter or "e" without .split

java

eclipse

input

while-loop

java.util.scanner