Question

我正在学习如何在Java中使用Scanner，我想从stdin读取一个整数和一个字符串，所以我写下面的代码：

import java.util.Scanner;

public class TryScanner {
    public void readInt() {
        Scanner in = new Scanner(System.in);
        System.out.println("Please type in an integer");
        int length = in.nextInt();
        System.out.println("Integer you type is: " + length);
        in.close();

    }
    public void readString() {
        Scanner in = new Scanner(System.in);
        System.out.println("Please type in a string");
        String s = in.nextLine();
        System.out.println("String you type is: " + s);
        in.close();

    }
    public static void main(String[] args) {
        TryScanner instance = new TryScanner();

        instance.readInt();
        // throw exception when called after readInt()
        instance.readString();
    }
}

我的readInt和readString函数分别运行良好，但是，当我按顺序调用它们时，只有第一个函数有效，第二个函数抛出异常：

Please type in an integer
3
Integer you type is: 3
Please type in a string
Exception in thread "main" java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Scanner.java:1597)
    at helloworld.Sort.readString(Sort.java:17)
    at helloworld.Sort.main(Sort.java:27)

有人可以解释我做错的地方吗？

Answer 1

删除对

的调用

array

当您关闭in.close();时，您还in close全局（并且它不会重新打开）。

System.in

另外，您可以考虑将public void readInt() { Scanner in = new Scanner(System.in); System.out.println("Please type in an integer"); int length = in.nextInt(); System.out.println("Integer you type is: " + length); // in.close(); } public void readString() { Scanner in = new Scanner(System.in); System.out.println("Please type in a string"); String s = in.nextLine(); System.out.println("String you type is: " + s); // in.close(); }传递给方法。

Scanner

Answer 2

您也可以使用以下代码

import java.util.Scanner;

public class TryScanner {
    Scanner in = new Scanner(System.in);

    public void readInt() {

        System.out.println("Please type in an integer");
        int length = in.nextInt();
        System.out.println("Integer you type is: " + length);

    }

    public void readString() {
        System.out.println("Please type in a string");
        String s = in.nextLine();
        System.out.println("String you type is: " + s);

    }

    public static void main(String[] args) {
        TryScanner instance = new TryScanner();

        instance.readInt();
        instance.readString();
        instance.in.close();
    }
}

使用Java Scanner按顺序从stdin读取时抛出异常

2 个答案: