Substring search in Java

Question

i am having a problem with string comparison. For example, I have 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);
}

Answer 2

For an exact String comparison, you can simply do:

boolean match = stringA.equals(stringB);

If you want to check that a string contains a substring, you can do:

boolean contains = string.contains(substring);

For more String methods, see the javadocs