Help with error!!

I am using openjdk on Ubuntu and I am trying to wright the following program:

public class use
{
public static void main(String[] args)
{
System.out.print ("hi");
System.out.println(args[0]);
System.out.println("gal");
}
}

I got the program out of a handbook, but I constantly get the following error:

hiExeption in thread "main" java.lang.ArrayIndexOutOfBoundsExeption:0 at use.main(use.java:11)

Ok, first of all, naming convention states that class names should begin with uppercase, just a nitpick, but it's good to get the right habits right off the bat. Now, your error pops up, because of this line:

Code:

---

System.out.println(args[0]);

---

args stores command line parameters used when you launch the program, so for instance, if you ran a program like this:
java MyProg one two three
values in the args array would be as follows:
args[0] = "one";
args[1] = "two";
args[2] = "three";
You ran your program without any parameters, and so the args array was not initialised, and you tried to print out an undeclared value. To avoid this kind of problem, do this:

Code:

---

public class Use { //note the uppercase
  public static void main(String[] args) {
      if(args.length == 0) {
          System.out.println("Usage: java Use yourname");
          System.exit(1); //nonzero exit values mean program terminated because of error
      }
      System.out.println("hi "+args[0]+" gal");
  }
}

---

Now, if you run this program without a parameter (java Use), the output would be the usage, then the program quits, and doesn't terminate with an exception.

If I use the program it always exits, how do I get the args.length longer so that it doesn't exit.

Quote:

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Originally Posted by hellolleh

If I use the program it always exits, how do I get the args.length longer so that it doesn't exit.

---

Pass a command line argument to your class, your code expects at least one argument:

Code:

---

java -cp . use hellolleh

---

kind regards,

Jos

sorry I don't understand? :confused:

My post contains an example. Read it, don't just copy and paste the code.

run your code with line

System.out.println(args.length);

instead of
System.out.println(args[0]);

if you do that, it will show the array length 0(means its empty). but u r trying to print the 0th element(1st element in array) which is not there. thats why its exception.ou
So, inorder to print the 1st element in array, you need to insert into array. So you do that
from command line.

look at josah's suggestion.