Java从命令行参数读取并打印文件

Question

Accept command line argument for a string to open a text file and print its contents. Text file is like a dictionary: a list of words separated by new lines.

Using other examples this is what I've tried to no success. Do not use any java collections/libraries outside these ones.

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
class test{
public static void main(String[] args) {
  File file = new File(args[0]);
   try {    
        Scanner sc = new Scanner(file);
        while (sc.hasNextLine()) {
            int i = sc.nextInt();
            System.out.println(i);
        }
        sc.close();
    }
   catch (FileNotFoundException e) {
        e.printStackTrace();
}
}
}

Answer 1

Unless your file contains int(s), calling sc.nextInt() is not correct; and when it is correct, you would want to use sc.hasNextInt() (not sc.hasNextLine() ). Here, you want to use sc.nextLine() to read each word (since there is one per line). Also, you should check that the file exists before attempting to read from it (so you can handle that condition reasonably). Finally, I would prefer try-with-Resources over explicitly managing the life-cycle of your Scanner . Like,

File file = new File(args[0]);
if (!file.exists()) {
    try {
        System.err.printf("Could not find '%s'.%n", file.getCanonicalPath());
        System.exit(1);
    } catch (IOException e) {
        e.printStackTrace();
    }
}
try (Scanner sc = new Scanner(file)) {
    while (sc.hasNextLine()) {
        String line = sc.nextLine();
        System.out.println(line);
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
}