TIOBE - Java Coding Standard

Rule: StringandStringBuffer9

Synopsis:	String.indexOf(char) is faster than String.indexOf(String)
Language:	Java
Severity Level:	4
Category:	StringandStringBuffer

Description:

Use String.indexOf(char) when checking for the index of a single character; it executes faster.

public class Foo {
 void bar() {
  String s = "hello world";
  // avoid this
  if (s.indexOf("d") {}
  // instead do this
  if (s.indexOf('d') {}
 }
}