Command line arguments help

[may88]

Hi i am very new to java and have just written this basic piece of code

import java.util.Scanner;
import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import javax.imageio.imageIO;
import.java.awt.Color;
public class FinalExam
{
public static void main(String [] args) throws IOException
{
Scanner keyboardInput = new Scanner(System.in);
System.out.print("Input the address of the image (e.g. c:\\myPicture.jpg)");
String imageLocation = keyboardInput.nextLine();
File imageFile = new File(imageLocation);
BufferedImage storedImage = ImagIO.read(imageFile);




does anyone know how you would change the code to supply the name of an image file as a command line argument, when running the program?

[sky]

In the array args are stored the command line arguments. Just change ImageLocation for args[0]. You also should check if the length of the array is 1.

[gcampton]

In the array args are stored the command line arguments. Just change ImageLocation for args[0]. You also should check if the length of the array is 1.

I'm pretty sure program name is always stored in args[0]
so it would be args[1]

or I could be getting confused with c/c++ and unix scripting.

you will just have to test this.

[gcampton]

here's some sample code you can use to test:

public static void main(String [] args)
{
   for ( int i=0; i < args.length; i++ )
   {
      System.out.printf("%d.\t%s\n", i, args[i]);
   }
}

now if you run this program using:

$ program hello world my name is Bob

// the output should be:

0. program
1. hello
2. world
3. my
4. name
5. is
6. Bob

EDIT: sorry I am wrong, was thinking of c++/unix. the output would be

0. hello
1. world
2. my
3. name
4. is
5. Bob

[sky]

Yes, in C te name of the program is stored in argv[0], and also another parameter is passed indicating the number of arguments (argc)

[gcampton]

yep, and in sh/bash/ksh/csh/zsh/ash/dash etc etc etc...

$0 is always the program name, even after shifting positional parameters.

I would think java would take after this convention, seems pretty silly not to.

[masijade]

Nope, it doesn't though. The args array are truely those, just the arguments (i.e. everything entered after the name of the main class).

[gcampton]

yea there was probably a meeting that went something like this:

p1: I think we should keep to the C convention of command line args.

p2: name one good use for having program name stored in 0.

p1: errrrrr......ahhhhhhhh, hmmmmm.

p2: motion granted, args[0] will not contain filename...

[masijade]

They have made some rather stranger decisions though, IMHO. Take Calendar for instance. The months "array" starts with 0 like in nearly every other language I've seen, but the weekdays "array" starts with 1, why?

public class CalendarQuestions {

	public static void main(String[] args) {
		System.out.println("January:    " + Calendar.JANUARY);
		System.out.println("February:   " + Calendar.FEBRUARY);
		System.out.println("March:      " + Calendar.MARCH);
		System.out.println("April:      " + Calendar.APRIL);
		System.out.println("May:        " + Calendar.MAY);
		System.out.println("June:       " + Calendar.JUNE);
		System.out.println("July:       " + Calendar.JULY);
		System.out.println("August:     " + Calendar.AUGUST);
		System.out.println("September:  " + Calendar.SEPTEMBER);
		System.out.println("October:    " + Calendar.OCTOBER);
		System.out.println("November:  " + Calendar.NOVEMBER);
		System.out.println("December:  " + Calendar.DECEMBER);
		System.out.println();
		System.out.println("Sunday:     " + Calendar.SUNDAY);
		System.out.println("Monday:     " + Calendar.MONDAY);
		System.out.println("Tuesday:    " + Calendar.TUESDAY);
		System.out.println("Wednesday:  " + Calendar.WEDNESDAY);
		System.out.println("Thursday:   " + Calendar.THURSDAY);
		System.out.println("Friday:     " + Calendar.FRIDAY);
		System.out.println("Saturday:   " + Calendar.SATURDAY);
	}
}