Using args [0] in Eclipse

Question

    import java.util.Scanner;

    public class argu {

public static void main(String[] args) 
{
    int number = Integer.parseInt(args [0]);
    int x = number % 2;

    if (x == 0) {
        System.out.println("It is even");

    }
    else {
        System.out.println("It is not even");
    }
        }
    }

I have been trying to code this program to make an user enter a number, (that is the args [0] for), however, it sends this error.

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at argu.main(argu.java:7)

The fix I made was

    import java.util.Scanner;

    public class argu {

        public static void main(String[] args) 
        {
            Scanner scan = new Scanner (System.in);

    int number = scan.nextInt();
    int x = number % 2;

    if (x == 0) {
        System.out.println("It is even");

    }
    else {
        System.out.println("It is not even");
    }
        }
    }

I want to know if there is a way to user args [0] instead of the Scanner method. Keep in mind, I am a beginner, so I am sorry some of the stuff is wrong

My other question is to help me analyze the method Scanner scan = new Scanner (System.in);

scan is the variable? Scanner is the method? I am confused with variables, parameters, and methods. If you could help me differentiate one from the other.

Thank you.

Answer 1

args[0] indicates the arguments when used to start up the program - this is done using commands.

Say you ran this command through cmd or the terminal:

java -jar myjar.jar 5

The value of args[0] would be 5, because 5 in the command is an argument. The argument is passed to args[]. Adding another argument would go to args[1]:

java -jar myjar.jar 5 10

args[1] would equal 10.

See @Ruets answer for details on how to use arguments in Eclipse.

You get your error because args[0] is not existent - the command would look more something like this:

java -jar myjar.jar

Answer 2

In eclipse to add an argument to the program you have to add a run configuration with that argument.

That's in the Run -> Run Configurations... -> pick your configuration (probably "main" or "argu") -> Arguments (tab) -> add arguments in Program Arguments (top text field, Name your configuration something meaningful).

Now use this configuration to run the program. You can have many different configurations obviously.