indexOf

[Kamil Dada]

Hello, please take a look at this code:
1 class strings
2 {
3 public static void main(String arg[])
4 {
5 if("String".indexOf("S",-10) ==0)
6 {
7 System.out.println("Equal");
8 }
9 else
10 {
11 System.out.println("Not Equal");
12 }
13 }
14 }
What does the indexOf method do, how do we use it, and how does the above code work?
Thank You,
Kamil

[Percy Densmore]

This is an interesting snippet. The method indexOf() returns a char from the index position or an int from the char position. Therefore, "String" => 012345
indexOf(char('S'), begin search fromIndex(-10))
if("String".indexOf("S",-10)==0) // Will (0,-10)==0?
{ // Run the code and find out!
System.out.println("Equal");
}
else
{
System.out.println("Not Equal");
Hope that helps a little,
Percy

[Vanitha Sugumaran]

Hi,
5 if("String".indexOf("S",-10) ==0)
if the second argument is negative value it is treated as 0. So the entire String is searched and it returns 0 because the indexOf "S" is 0.
0==0 is true so it prints Equals.

From API
public int indexOf(String str,
int fromIndex)
Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. The integer returned is the smallest value k such that:
this.startsWith(str, k) && (k >= fromIndex)

is true.
There is no restriction on the value of fromIndex. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: -1 is returned.

Vanitha.