1.java

public class NaturalLog {

  public static void main(String args[]) {
    System.out.println(getNaturalLog());
  }

  static double getNaturalLog() {
    int index = 1;
    double item = 1;
    double result = 0;

    while (item >= 1e-4)
    {
      result += item;
      item /= index++;
    }

    return result;
  }
}