count two following x with overlapping

WarmUp.java

class Main{
int countXX(String str) {
  boolean lastOneIsX = false;
  int countXX = 0;
  for(int i=0;i<str.length(); i++){
    if(str.charAt(i)=="x".charAt(0)){
      if(lastOneIsX){
        countXX++;
      }
      lastOneIsX = true;
    }else{
      lastOneIsX=false;
    }
  }
  
  return countXX;
}
  
 boolean doubleX(String str) {
   
   /*
   boolean doubleX(String str) {
  int i = str.indexOf("x");
  if (i == -1) return false; // no "x" at all

  // Is char at i+1 also an "x"?
  if (i+1 >= str.length()) return false; // check i+1 in bounds?
  return str.substring(i+1, i+2).equals("x");
  
  // Another approach -- .startsWith() simplifies the logic
  // String x = str.substring(i);
  // return x.startsWith("xx");
}
   */
   
  int firstXIndex = str.indexOf("x");
  if(firstXIndex == str.length()-1)return false;
  if(str.charAt(firstXIndex+1)=="x".charAt(0)) return true;
  
  return false;
}


}

int countXX(String str) {
int count = 0;
for (int i = 0; i < str.length()-1; i++) {
if (str.substring(i, i+2).equals("xx")) count++;
}
return count;
}