Substring search in Java

Question

I have a problem with string comparison. For example, there is this string:

"hello world i am from heaven"

I want to search if this string contains "world". I used following functions but they have some problems. I used String.indexof() but if I will try to search for "w" it will say it exists.

In short I think I am looking for exact comparison. Is there any good function in Java?

Also is there any function in Java that can calculate log base 2?

Answer 1

I'm assuming the problems you're having with indexOf() related to you using the character version (otherwise why would you be searching for w when looking for world?). If so, indexOf() can take a string argument to search for:

String s = "hello world i am from heaven";
if (s.indexOf("world") != -1) {
  // it contains world
}

as for log base 2, that's easy:

public static double log2(double d) {
  return Math.log(d) / Math.log(2.0d);
}