How does this method work?

[Olivier Legat]

public class MainClass {
  public static void main(String args[]) {
  String s = "This_is_an_demo.";
  int start = 1;
  int end = 5;
  char buf[] = new char[end - start];
  s.getChars(start, end, buf, 0);
  System.out.println(buf);
  }
}

The output is "his_".

What is the variable buf[] for? My teacher told me to put it but I don't know why!

Another thing I don't understand is why does it stop at the first "_"? Shouldn't it display "his_i"? (i.e. Up until index 5 since int end=5)

[Raghavan Muthu]

Originally posted by Olivier Legat:

What is the variable buf[] for? My teacher told me to put it but I don't know why!

The variable "buf" with the pair of square brackets "[]" means an array! A set of contiguous memory locations being used to store the similar kinda data value. Here in this case, you use a container to store a set of characters. so you need an array of characters.

In Java, you declare the array in this way!

Another thing I don't understand is why does it stop at the first "_"? Shouldn't it display "his_i"? (i.e. Up until index 5 since int end=5)

Well, end is 5 and start is 1. so, (end-start) will give you 4 (5-1=4 ). As the arrays always start with 0 instead of 1, you will get upto 4.

Does that help?

[Rob Spoor]

Also, in nearly all API calls that need an end index, this end index is exclusive. So if you want characters 1 to 5, you need to give the end as 6.

[Olivier Legat]

YAH! Helps loadz. Thanks