Java program to find the longest substring of vowels .
import java . util . * ; class GFG { static boolean isVowel ( char c ) { return ( c == ' a ' c == ' e ' c == ' i ' c == ' o ' c == ' u ' ) ; } static int longestVowel ( String str ) { int count = 0 , res = 0 ; char [ ] s = str . toCharArray ( ) ; for ( int i = 0 ; i < s . length ; i ++ ) {