Returns the index within this string of the first occurrence of the specified character. If a character with value
ch occurs in the character sequence represented by this
String object, then the index (in Unicode code units) of the first such occurrence is returned. For values of
ch in the range from 0 to 0xFFFF (inclusive), this is the smallest value
k such that:
this.charAt(k) == ch
is true. For other values of
ch, it is the smallest value
k such that:
this.codePointAt(k) == ch
is true. In either case, if no such character occurs in this string, then
-1 is returned.
@param ch a character (Unicode code point).
@return the index of the first occurrence of the character in thecharacter sequence represented by this object, or
-1 if the character does not occur.