java - 扫描仪永远不会停止从键盘读取

Question

下面的代码为什么会进入无限循环？我以为它会显示我输入的第一个短语，但他从未停止从键盘上阅读。1-为什么？2-如何才能只读一次？

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        System.out.println("Type anything: ");

        while(scan.hasNext()) {
            System.out.println("Token: " + scan.next());
        }

        System.out.println("-------------------------");
        scan.close();
    }
}

Answer 1

扫描仪正在等待“文件结束”条件，我只能通过使用扫描仪读取文件来获取此 EOF 条件。如果您只想读取输入一次并打印它，那么您可以执行以下操作:

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);

    System.out.println("Type anything: ");
    System.out.println("Token: " + scan.next());
    System.out.println("-------------------------");
    scan.close();
}

您还可以给它一个停止条件:

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);

    System.out.println("Type anything: ");
    String input = scan.next();

    while(!input.equals("exit")){
        System.out.println("Token: " + input);
        System.out.println("\nType anything: ");
        input = scan.next();
    }
    scan.close();
}

我以前从文件中读取的内容:

public static void main(String[] args) {

    File file = new File("random_text_file.txt");

    try {

        Scanner scanner = new Scanner(file);

        while (scanner.hasNext()) {
            String word = scanner.next();
            System.out.println(word);
        }
        scanner.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}