Using only 0's to the left of E forces no decimal point : NumberFormat « I18N « Java Tutorial

1. Java Tutorial
2. I18N
3. NumberFormat

import java.text.DecimalFormat;
import java.text.NumberFormat;

public class Main {
  public static void main(String[] argv) throws Exception {

    NumberFormat formatter = new DecimalFormat("0E0");
    String s = formatter.format(-1234.567);
    System.out.println(s);
  }
}
// -1E3