how to find the second occurrence of a character in java code example

Example 1: how to get index of second occurrence java

String str = "itiswhatitis";
//returns the index of the first i in "is"
str.indexOf("is");
//returns the index of the second occurence of  i in "is" after the first 
str.indexOf("is", str.indexOf("is") + 1);

Example 2: java indexof nth occurrence

public static int ordinalIndexOf(String str, String substr, int n) {
    int pos = str.indexOf(substr);
    while (--n > 0 && pos != -1)
        pos = str.indexOf(substr, pos + 1);
    return pos;
}