代码

		double doub = -54450.0;

		Calendar calStart = Calendar.getInstance();
		long start = calStart.getTimeInMillis();
		System.out.println("开始时间：" + start);
		for (int i = 1; i <= 1000000000; i++)
		{
			if (doub < 0) // 311毫秒
			// if (doub < 0.0)// 共用时306毫秒

			{
				// System.out.println("小于0");
			}
		}
		Calendar calEnd = Calendar.getInstance();
		long end = calEnd.getTimeInMillis();
		System.out.println("结束时间：" + end);
		System.out.println("共用时" + (end - start) + "毫秒");

结果：两者时间差不多