Explain me please

[surekha raju]

Anyone please let me know the output of both...
executed by entering "java test lets see what happens".
1.public class test {
public static void main(String args[]) {
System.out.println(args[0]+" "+args[args.length-1]);
}
}

Answer for this is:lets happens

2.
public class test {
public static void main(String args[]) {
System.out.println(args[0]+" "+args[args.length]);
}
}


answer is:The program will throw an ArrayIndexOutOfBounds exception

[Deepak Bala]

The array indexes are zero based. For the first program the args.length variable gives you a value whose index is out of bounds. args.length - 1 will give you the last element in the array and args[0] gives you the first element in the array ( considering that you pass atleast one element in the command line).

Example: java test 1 2

here args[0] = 1 and args[1] = 2 and args.length = 2 so args.length-1 gives you the value of the last element.

[Charles Lyons]

Sorry, I was obviously writing this at the same time as John...

Anyone please let me know the output of both...

Since you've supplied the output, I assume you actually don't mean that! As far as explanation goes:

In the first example, there are 4 command line arguments { "lets", "see", "what", "happens" }, but these are referenced on a 0-based index, so in fact although there are 4 entries, they are actually indexed by 0, 1, 2, 3. So in the println() argument we have:

args[0] which references "lets" as the first entry
args[args.length - 1] == args[4-1] == args[3] which references "happens"

So you see, the last index is the length of the array subtract 1.

In the second example, you attempt to access args[args.length], but this is always out of range, because the last index is always (args.length - 1) and not args.length.

Using the previous command line data we would be trying to reference:

args[args.length] == args[4] which does not exist!

Therefore an ArrayIndexOutOfBounds is thrown. Does that make sense? If it's array indexing that troubling you, remember that arrays are 0-based, not 1-based as our counting usually is; we count 1, 2, 3..., arrays count 0, 1, 2... and so the last index is one less than the length.
[ April 16, 2006: Message edited by: Charles Lyons ]

[surekha raju]

thanks for ur explanation...i wont go wrong in future...