Use new DecimalFormat("0.#####E0") to format double : Decimal « Data Type « Java Tutorial

1. Java Tutorial
2. Data Type
3. Decimal

import java.text.DecimalFormat;

public class Main {
  public static void main(String args[]) {
    double d = 0.12345;

    System.out.println(new DecimalFormat("0.#####E0").format(d));
  }
}
//1.2345E-1