java.util.NoSuchElementException没有这样的元素异常

时间:2013-02-27 10:34:03

标签: java

Java新手 - 只是试图掌握它。该程序正在执行如下:

What's your age?23
23
What's your name?Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at king.getName(king.java:25)
    at king.main(king.java:9)

它试图运行的代码如下:

import java.util.*;

public class king {



    public static void main(String[] args){
        System.out.println(getAge());
        System.out.println(getName());
    }

    public static int getAge(){
        System.out.print("What's your age?");
        Scanner scanner = new Scanner(System.in);
        String age = scanner.next();
        scanner.close();
        int numberAge = Integer.parseInt(age);
        return numberAge;

    }

    public static String getName(){
        System.out.print("What's your name?");
        Scanner newScanner = new Scanner(System.in);
        String name = newScanner.next();
        newScanner.close();
        return name;
    }

}

4 个答案:

答案 0 :(得分:9)

请勿使用scanner.close()< - 错误来源!

删除行scanner.close()newScanner.close()

来自Java DOC:

  

当扫描仪关闭时,如果是源,它将关闭其输入源   实现Closeable接口。

这意味着它会关闭System.in - 糟糕的选择!

从JDK中Scanner.java的源代码,throwFor()是:

private void throwFor() {
    skipped = false;
    if ((sourceClosed) && (position == buf.limit()))
        throw new NoSuchElementException();
    else
        throw new InputMismatchException();
}

显然,如果我们已经到达输入的末尾,或者如果源被关闭,那么我们得到NoSuchElementException()。我很确定因为position == buf.limit()而不是sourceClosed

IDEONE发生了{{}}}

答案 1 :(得分:1)

试试这个:

public class King {
  public static void main(final String[] args) {
    final Scanner scanner = new Scanner(System.in);
    System.out.println(getAge(scanner));
    System.out.println(getName(scanner));
  }

  public static int getAge(final Scanner scanner) {
    System.out.print("What's your age?");
    final String age = scanner.next();
    final int numberAge = Integer.parseInt(age);
    return numberAge;
  }

  public static String getName(final Scanner scanner) {
    System.out.print("What's your name?");
    final String name = scanner.next();
    return name;
  }
}

另请注意,java类应该大写。

答案 2 :(得分:1)

我认为alraedy @Aniket给出了一个非常好的答案。

  • 首先,您可以使用import java.util.*;代替import java.util.Scanner;,因此不会导入不必要的类。
  • 第二件事是你可以像我在示例中看到的那样Scanner。(所以你可以关闭它)

     import java.util.Scanner;
     public class SO6 {
         static Scanner scanner = new Scanner(System.in);
         public static void main(String[] args){
             System.out.println(getAge());
             System.out.println(getName());
             scanner.close();
         }
    
        public static int getAge(){
            System.out.print("What's your age?");
            String age = scanner.next();
            int numberAge = Integer.parseInt(age);
            return numberAge;
    
        }
    
        public static String getName(){
            System.out.print("What's your name?");
            String name = scanner.next();
            return name;
        }
    }
    

答案 3 :(得分:1)

首先,为了避免NoSuchElementException,您应该在使用Scanner.next()之前执行Scanner.hasNext()检查。其他评论,尤其是关于使用单个扫描仪的评论也很有用。