How do I input a file name that is read in command line arguments? [duplicate]

Say, you invoke your program as

java MyMainClass /path/to/file

Then in the main() method just use

File f = new File(args[0])

Then, you might want to validate that

f.exists()
f.isFile()
f.canRead()

etc.

To actually read the file you can follow those instructions as suggested in the comment by @Kevin Esche

java MainClass <list of arguments>

Now in main class you will receive all the argument in String array, which is passed in the main method.

public static void main(String args[]) {
   for(String argument : args) {
     System.out.println(argument);
   }
}

When running a java program from the console you call:

java programName list of inputs separated by space

So in your case you have:

java Project inputFile.txt

When the JVM starts and calls main() it will take everything after your project name and create a String array of that separated by the spaces.

So in my first caommand line I would get:

{"list" + "of" + "inputs" + "separated" + "by" + "space"}

This string array will come into your program in the main function:

public static void main(String[] args) { ... }

Therefore, in your case, args[0] will be the file name you are looking for. You can then create a file reader of sorts. If you don't add any path to the front of the file name it will look for the file in the folder that your src folder is in.

Hope this helps.

Maybe this would help, it reads and prints the file to the console.

public static void main(String[] args) {
    File f=  new File(arg[0]);

    InputStream is = new FileInputStream(f);

    int byteReaded;

    while ((byteReaded = is.read())!=-1) {
       System.out.print((char)byteReaded);

    }
}