Javaは配列に要素が含まれているかどうかを判断します

public static boolean useList(String[] arr, String targetValue) {
  return Arrays.asList(arr).contains(targetValue);
}

public static boolean useSet(String[] arr, String targetValue) {
  Set<String> set = new HashSet<String>(Arrays.asList(arr));
  return set.contains(targetValue);
}

public static boolean useLoop(String[] arr, String targetValue) {
  for(String s: arr){
    if(s.equals(targetValue))
      return true;
  }
  return false;
}

public static boolean useArraysBinarySearch(String[] arr, String targetValue) { 
  int a = Arrays.binarySearch(arr, targetValue);
  if(a > 0)
    return true;
  else
    return false;
}