Method Signature:
	public int indexOf(String str)
	public int indexOf(String str, int fromIndex)
	public int indexOf(char c)
	public int indexOf(char c, int fromIndex)

Returns: Index of the first occurrence of the passed argument
		-1 if it never occurs

Eg: String myStr = "Hello World!";
	System.out.println(myStr.indexOf("o"));
Output: 4

The java string indexOf() method returns index of given character value or substring. If it is not found, it returns -1. The index counter starts from zero.