passing input file in java through command line

Question

 FileInputStream fstream = new FileInputStream("textfile.txt");

This is above code to get the input file , i want a input file to give from command line

ie pseudo command line code

java  filename giveinputfile("textfile.txt")

What change i modify in my java code and command line(windows) to make this work

Answer 1

You use the String[] args in your main method,

public static void main(String[] args) {
  String fileName = "textfile.txt";
  if (args.length > 0) { 
    fileName = args[0];
  }
  System.out.println("fileName: " + fileName);
}

Then you run your program with

java myProgram MY_FILE

or

java myProgram

With the code above the first command would use "MY_FILE" and the second would use the default "textfile.txt".