How to find indexof in a string

public static void main(String[] args) {
		// TODO Auto-generated method stub
		String str = "567890432";
		dd d = new dd();
		System.out.println(d.findindexof(str, 2));
// value at index 2 is 6

	}

	public int findindexof(String str, int a) {

		for (int i = 0; i < str.length(); i++) {
                if(){}
			//what would be code over here

		}
		return 0;
	}
}