从命令行Java编译并运行

Question

I'm working on a project for one of my classes. And the program its self is not so much the problem as is way that it will be tested. I have no experience working with the command line, and that is how my program will be test.

I created a hill cipher program. The inputs are a key file and a plaintext file. The command line entry will look like this.

prompt> java hillcipher spr16Key4.txt hill-16spring-01

How can I do this? Can I modify this code so that it will work with the above command?

try{ 
        //open plaintext file
        URL url = getClass().getResource("input.txt"); //.getResource(args[0]);?
        File file = new File(url.getPath());
        //used to move data on the encryption path
        sc  = new Scanner(file);

        }catch(Exception e){

        System.out.println("file not found.");

    }

Answer 1

The program needs a couple of minor changes:

• class.getResource() will only scan for the file in class path. To read the external file, we can use the file constructor that takes a string argument. Eg File file = new File(args[0]);
• The arguments while running the program need to be changed to full paths (like java hillcipher "D:/spr16Key4.txt" "D:/hill-16spring-01" so that the program would be able to read the files even if they are not in the same directory as class file.

Answer 2

You can create a common method for processing the contents of your file. For that do the following:

public class HillCipher {
    public static void main(String[] args) {
        String keyFile = args[0];
        String plainFile = args[1];

        // Read your key file
        processFile(keyFile);

        // Read plain file
        processFile(plainFile);
    }

    private static void processFile(String filePath) {
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
            String line = br.readLine();

            while (line != null) {
                // do what you need with the file contents
                System.out.println(line);
                line = br.readLine();
            }
        }
    }
}

In order to run it, just do what you mentioned, taking into account the file paths:

>java HillCipher key_file.txt plain_file.txt