Passing values to main(String args[]) ?

Hi, I saw some code which appeared to pass values to void main(String args[])
and I was wondering how this is done and why it would be done.

example:

Code:

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 public static void main(String args[]) {
    if (args.length < 2) {
      System.out.println("some message");
    }

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Also, where exactly in code do you call the void main(String args[]) function. :confused: I have never seen anything like for example:

Code:

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String str="hello";
if(someCondition==true)
{
main(hello);
}

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Thanks in advance for any help :)

If you have a program Hello.java which you compile to Hello.class, you pass these parameters (known as command line parameters) when you call the program:

c:\java>java Hello this is a command line parameter

java Hello is calling your program and all that follows are the command line parameters.

when you can any java file from command line you can pass arguments. If length of the command line arguments is less than 2 then it will print that message.

Quote:

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Originally Posted by Fubarable

If you have a program Hello.java which you compile to Hello.class, you pass these parameters (known as command line parameters) when you call the program:

c:\java>java Hello this is a command line parameter

java Hello is calling your program and all that follows are the command line parameters.

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Ok so let me see if I understand. If I were to write c:\java>java Hello
then args[0] would contain nothing?

but if I were to write c:\java>java Hello msg
then args[0] would be msg.

I have just used run configuration in eclipse and used (x)=Arguments option and wrote something in there and ran the program and args.length printed 1. Is this the same idea as the command line parameter pass?

Quote:

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Originally Posted by al_Marshy_1981

I have just used run configuration in eclipse and used (x)=Arguments option and wrote something in there and ran the program and args.length printed 1. Is this the same idea as the command line parameter pass?

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Yes indeed.

Thanks Fubarable.

Quote:

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Originally Posted by al_Marshy_1981

Ok so let me see if I understand. If I were to write c:\java>java Hello
then args[0] would contain nothing?

but if I were to write c:\java>java Hello msg
then args[0] would be msg.

I have just used run configuration in eclipse and used (x)=Arguments option and wrote something in there and ran the program and args.length printed 1. Is this the same idea as the command line parameter pass?

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Hallo Marshy

if you don't pass any parameters and you ask for args[0] then you will get a OutOfBoundsExeption. So, to avoid this, use this for-example

Code:

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                for (int i = 0; i < args.length; i++) {
                        System.out.println(args[i]);
                }

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Even if no parameter are passed no exception will be thrown and you don't have to care how many parameters are passed, because all will be processed in the for-loop.