从命令行传递文件 Java

Question

So I have a file of integers, one in every line and I want to pass the file as input through args[0] from the command line. When I write at the command line java Sorting input.txt I just get "input.txt". But when I write java Sorting 3 2 6 i correctly get 2 3 6. How am I supposed to pass the file? The code is below:

import java.util.Arrays;
public class Sorting {
public static void main (String args[])
{


    Arrays.sort(args);
    for(String num: args)
        System.out.println(num);
}

}

Answer 1

args[] is just the list of arguments - if you pass in a file, the filename is the argument.

Haven't run this, but try something like:

public static void main (String args[])
{

    String filename = args[0];

    // Read the file content to a String
    String fileContent = Files.readString(Paths.get(filename));

    // Split on whitespace (this is a regex, whitespace is \\s in Java - could also use " " for just space)
    // The '+' here denotes "at least 1" whitespace character - added after the discussion below
    String[] elements = fileContent.split("\\s+");
    Arrays.sort(elements);

    for(String num: args)
        System.out.println(num);
}

== Edit==

If you want them sorted as integer's you're correct to say that the above treats them as String s. You need to parse them as Int for that:

public static void main (String args[]) {

    String filename = args[0];

    // Read the file content to a String
    String fileContent = Files.readString(Paths.get(filename));

    // Split on whitespace (this is a regex, whitespace is \\s in Java - could also use " " for just space)
    // The '+' here denotes "at least 1" whitespace character - added after the discussion below
    String[] elements = fileContent.split("\\s+");
    int[] intElements = new int[elements.length];
    for (int i = 0; i < elements.length; i ++) {
        try {
            intElements[i] = Integer.parseInt(elements[i]);
        } catch (NumberFormatException ex) {
            System.err.println("Not a number: " + elements[i]);
        }
    }
    Arrays.sort(intElements);

    for(int num: intElements)
        System.out.println(num);

}