Java文件结束

任务：每行将包含一个非空字符串。读到EOF。 对于每一行，打印行号，后跟一个空格和行内容

样本输入：

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner line = new Scanner(System.in);
        int counter = 1;
        
        while (line.hasNextLine()) {
            String line = line.nextLine();

            System.out.println(counter + " " + line);
            counter++;
        }
    }
}

样本输出：

Hello world

I am a file

Read me until end-of-file.

---

要读取用户输入，您需要在代码中的

行

对象声明中使用

系统

1 Hello world

2 I am a file

3 Read me until end-of-file.

说明您需要将
源代码
传递给扫描仪，以便扫描仪可以从中进行扫描

若要获取用户输入，则需要使用构造函数

Scanner line = new Scanner(System.in);
int counter = 0; // Initialized out of loop.
while (line.hasNextLine()) {
  String ln = line.nextLine();
  System.out.println(counter  +" "+ln);
  counter++;
}

Scanner line = new Scanner(); // <-- YOUR ERROR - there is no constructor for the Scanner object that takes 0 arguments. 
// You need to specify the environment in which you wish to 'scan'. Is it the IDE? A file? You need to specify that.


注意：确保
中断
while循环，否则它将进入
无限循环。
如果要从文件扫描，可以使用以下代码

public static void main(String[] args) {
    Scanner line = new Scanner(System.in); // Added source parameter in constructor.
    int counter = 1; // Initialization of counter is done outside while loop, otherwise it will always get initialized by 1 in while loop
    while (line.hasNextLine()) {
        String lineStr = line.nextLine(); // changed variable name to lineStr, because 2 variable can't be declared with the same name in a method.
        System.out.println(counter + " " + lineStr);
        counter++;
    }
}

如果没有相同的名称，则不能有多个变量。您必须重命名一个
行
变量
创建扫描仪时，您需要发送希望从中读取的输入流。System.in can服务器作为此流，它将从控制台读取。不过，您的问题似乎表明您希望从文件中读取。如果确实要从文件中读取，则需要创建要从中读取的文件，并将该文件发送到扫描仪，以允许扫描仪从该文件中读取
尝试：

您还有一个名为：line的重复局部变量

我建议你多读一些书来掌握变量和对象是如何工作的，而不是猜测或者被你不懂的代码欺骗。这就是你成为一名优秀程序员的原因。
错误：找不到适合scannerScanner sc=new Scanner（System.in）的构造函数；另外，您正在初始化循环内的计数器变量。
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Solution {

    public static void main(String[] args) throws FileNotFoundException {
        Scanner scan = new Scanner(new File("input.txt"));
        int counter = 1;
        while (scan.hasNextLine()) {
            String line = scan.nextLine();
            System.out.println(counter + " " + line);
            counter++;
        }
    }
}

public class Solution {
    public static void main(String[] args) {

        //create the File
        File file = new File(filename);

        //send the file into Scanner so it can read from the file
        Scanner scanner = new Scanner(file);

        //initialize the counter variable
        int counter = 1;

        //read in the file line by line
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine();
            System.out.println(counter  +" "+ line);
            counter++;
        }
    }
}

Scanner line = new Scanner(); // <-- YOUR ERROR - there is no constructor for the Scanner object that takes 0 arguments. 
// You need to specify the environment in which you wish to 'scan'. Is it the IDE? A file? You need to specify that.

File readFile = new File(PATH_TO_FILE); // where PATH_TO_FILE is the String path to the location of the file
// Set Scanner to readFile
Scanner scanner = new Scanner(readFile);