New to Java

[JeremyLin]

Hello everyone, I'm starting to learn Java (only had 1 class till now but I already got some programs to work on) so bare with me.

My question is :

long i =Integer.parseInt(args[0]);

When I have this,

1. What does long mean ?

2. What's the whole Integer.parseInt(args[0]) part for ?

When I compile the program, I gotta write it like this {"5"} or else it won't work.

I have a function apart that does the factorial of a number so that's what the program is about.

Any help ?

Cheers!

[JosAH]

A long is like an int but it takes eight bytes so it can store much larger numbers. That args[0] mumbo jumbo converts a String (the first command line argument args[0]) to an int. You'll learn all about it in the next lessons.

kid regards,

Jos

[JeremyLin]

Thanks Jos.

I've understood the long part.

About the args[0] what will it convert to an int in this case ?
What's the purpose of using it in this case ?

Cheers!

[JosAH]

About the args[0] what will it convert to an int in this case ?
What's the purpose of using it in this case ?

The 'args' array is an array of Strings; it contains the command line arguments, so args[0] is the first command line argument (if it exists).

kind regards,

Jos

[JeremyLin]

The 'args' array is an array of Strings; it contains the command line arguments, so args[0] is the first command line argument (if it exists).

kind regards,

Jos

Hmm, thanks.
I don't think there exists any command line argument though :o

I mean, I do compile it using {"7"} so I'm guessing that would convert "7" to 7 right ?

[JosAH]

Hmm, thanks.
I don't think there exists any command line argument though :o

I mean, I do compile it using {"7"} so I'm guessing that would convert "7" to 7 right ?

Right; if there are no command line arguments the expression args[0] would cause your program to throw an ArrayIndexOutOfBoundsException and stop. Your version simply converts the String "7" to an int (which is 7 of course).

kind regards,

Jos

[JeremyLin]

Alright.
Thanks a lot Jos, I'll be posting some doubts I may have later :p

Cheers!