Question

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int iteam = sc.nextInt();
    Student[] students = new Student[iteam];
    int id;
    String name;
    String city, s_city;
    double marks, s_marks;

    for (int i = 0; i < iteam; i++) {
        id = sc.nextInt();
        name = sc.nextLine();
        city = sc.nextLine();
        marks = sc.nextDouble();
        students[i] = new Student(id, name, city, marks);

    }
}

我收到一个错误“ Exception in thread "main" java.util.InputMismatchException

    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at java.util.Scanner.nextDouble(Unknown Source)"

我也尝试使用next（），但存在相同的错误。并且我还导入了java.util.Scanner。

Answer 1

这里没有很多信息，但是我看到一个肯定会引起您问题的问题。

当您从一行中读取一个数字值，并期望用户按下回车键以提交该值时，您必须先消耗行尾，然后才能继续。扫描仪不会自动执行此操作。要让用户输入4个值，每次输入后都按回车键，您的输入循环应如下所示：

for (int i = 0; i < iteam; i++) {

    id = sc.nextInt(); sc.nextLine();

    name = sc.nextLine();

    city = sc.nextLine();

    marks = sc.nextDouble(); sc.nextLine();

    students[i] = new Student(id, name, city, marks);

}

Answer 2

以前的解决方案不正确。经过一些调试会话后，我想出了以下解决方案：

public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int iteam;
        iteam = sc.nextInt();
        Student[] students = new Student[iteam];
        int id;
        String name;
        String city;
        double marks;

        for (int i = 0; i < iteam; i++) {
            id = sc.nextInt();
            name = sc.next();
            city = sc.next();
            marks = sc.nextDouble();
            students[i] = new Student(id, name, city, marks);

        }
    }

为您提供一些解释：方法next()，nextInt()和nextDouble()扫描下一个标记作为输入值。但最重要的是Return不算在内，因为您的bash将此视为您的输入。

此外，您的键盘输入是本地解释的，特别是如果您想读取双精度字。例如，英文分隔符写为 DOT ，德语写为 COMMA 。

Answer 3

在读取4个值时，需要从输入中读取第一个int后调用sc.nextLine()。 Scanner#nextInt()仅读取整数，但不读取换行符"\n";您将需要使用Scanner#nextLine使用换行符。

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int iteam = sc.nextInt();
    Student[] students = new Student[iteam];
    int id;
    String name;
    String city, s_city;
    double marks, s_marks;
    for (int i = 0; i < iteam; i++) {
        id = sc.nextInt();
        sc.nextLine();//call next line to prevent exception
        name = sc.nextLine();
        city = sc.nextLine();
        marks = sc.nextDouble();
        students[i] = new Student(id, name, city, marks);
    }
}

完整的示例：

import java.util.Scanner;
public class MyClass {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int iteam = sc.nextInt();
        Student[] students = new Student[iteam];
        int id;
        String name;
        String city, s_city;
        double marks, s_marks;
        for (int i = 0; i < iteam; i++) {
            id = sc.nextInt();
            sc.nextLine();
            name = sc.nextLine();
            city = sc.nextLine();
            marks = sc.nextDouble();
            students[i] = new Student(id, name, city, marks);
        }
        for(Student s: students){
            System.out.println(s);
        }
    }
    private static class Student{
        private int id;
        private String name;
        private String city;
        private double marks;
        public Student(int id, String name, String city, double marks){
            this.id = id;
            this.name = name;
            this.city = city;
            this.marks = marks;
        }
        public String toString(){
            return "[Student] Id: "+this.id+", Name: "+this.name+", City: "+this.city+", Mark: "+this.marks;
        }
    }
}

正在获取错误消息“线程“ main”中的异常java.util.InputMismatchException”

3 个答案: