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String-2 > xyzThere - java

Return true if the given string contains an appearance of "xyz" where the xyz is not directly preceeded by a period (.). So "xxyz" counts but "x.xyz" does not. 


xyzThere("abcxyz") → true
xyzThere("abc.xyz") → false
xyzThere("xyz.abc") → true

Definiujemy loop ktory sprawdza za kazdym podejsciem czy kolejne indexy i,i+1 oraz i+2 i zdefiniowane dla nich char. 

Nalezy tu pamietac ze jesli sprawdamy po indeksach np i+2 to tzreba zostawic "miejsce" na koncu aby nie bylo outOfBoudnExeption tj przekroczenia rlugosci stringa.

Jezeli pierwszy warunek jest spelniony tj mamy na kolejnych indexach interesujace nas char-y sprawdzamy czy na poprzedzajacych nasza trojkę indexach pojawia sie "." zaczynamy od indexu 0 - tzreba to uwzglednić w warunku tj albo index 0 == 0 lub i-1 == 0


public boolean xyzThere(String str)
{
 int len = str.length() - 2;
 for(int i = 0; i < len; i++)
 {
  if(str.charAt(i) == 'x' && str.charAt(i+1) == 'y' && str.charAt(i+2) == 'z')
  {
   if(i == 0 || str.charAt(i-1) != '.')
    return true;
  }
 }
 return false;
}
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