How to determine negative number and positive number in Java？

This is Java code：

package com.test.day13.num;/** * @author BigBird * @date 2011-12-11 下午10:12:33 * @action 測試判斷一個數是正數還是負數 */public class NumTest { public static boolean positive(double f)   {       final boolean pos0[] = {true};       final boolean posn[] = {false, true};       if (f == 0.0)           return true;       while (true) {           // If f is in ]-1.0; 1.0[, multiply it by 2 and restart.           try {               if (pos0[(int) f]) {                   f *= 2.0;                   continue;               }           } catch (Exception e) {           }           // If f is in ]-2.0; -1.0] U [1.0; 2.0[, return the proper answer.           try {               return posn[(int) ((f+1.5)/2)];           } catch (Exception e) {           }           // f is outside ]-2.0; 2.0[, divide by 2 and restart.           f /= 2.0;       }   }   static void check(double f)   {       System.out.println(f + " -> " + positive(f));   }   public static void main(String args[])   {       for (double i = -10.0; i <= 10.0; i++)           check(i);       check(-1e24);       check(-1e-24);       check(1e-24);check(1e24);}}

The output is：

-10.0 -> false-9.0 -> false-8.0 -> false-7.0 -> false-6.0 -> false-5.0 -> false-4.0 -> false-3.0 -> false-2.0 -> false-1.0 -> false0.0 -> true1.0 -> true2.0 -> true3.0 -> true4.0 -> true5.0 -> true6.0 -> true7.0 -> true8.0 -> true9.0 -> true10.0 -> true-1.0E24 -> false-1.0E-24 -> false1.0E-24 -> true1.0E24 -> true