Binary search

 
public class Main{
  public static void main(String[] args) {
    double[] x = { -39, -3, 6, 10, 4, 9, 10 };

    double value = 8;
    int lower = 0, upper = x.length - 1;

    while (lower <= upper) {
      int middle = (lower + upper) / 2;

      if (value > x[middle])
        lower = middle + 1;
      else if (value < x[middle])
        upper = middle - 1;
      else
        break;
    }

    if (lower > upper)
      System.out.println("Not found");
    else
      System.out.println("Found");
  }
}
  

Not found