最小增加一倍

import java.text.ChoiceFormat;


public class Main {

  public static void main(String[] argv) throws Exception {
  /**来自 
   NowJava.com - 时  代  Java**/

    double d = 1.2;


    // Get the largest double less than d

    double d1 = ChoiceFormat.previousDouble(d); // 1.1999999999999997

    System.out.println(d1);


    // Get the smallest double greater than d

    double d2 = ChoiceFormat.nextDouble(d); // 1.2000000000000002

    System.out.println(d2);

  }

}