A Utility Function to find the common prefix between strings - str1 and str2
static String commonPrefixUtil ( String str1 , String str2 ) { String result = " " ; int n1 = str1 . length ( ) , n2 = str2 . length ( ) ; for ( int i = 0 , j = 0 ; i <= n1 - 1 && j <= n2 - 1 ; i ++ , j ++ ) { if ( str1 . charAt ( i ) != str2 . charAt ( j ) ) { break ; } result += str1 . charAt ( i ) ; } return ( result ) ; }