java - 查找数组中的下一个 double 值

Question

我正在编写一个 radio 调谐器的模拟程序。现在我想要一个可以以 0.05MHz 为步长循环遍历数组或数组列表的方法。目前，我有一个包含我最喜欢的 radio 频率的阵列，如果找到频率，则必须停止循环。

public static double favFrequencies [] = {89.8, 91.5, 93.7, 95.1, 97.7, 99.2, 100.7, 101.2, 101.7, 102.7, 103.0, 104.4};

目前我有以下代码:

public static void searchDown()
{
    double startFrequency = Math.round(currentFreq * 100);
    double maxFrequency = Math.round(87.80 * 100);
    for (double f = startFrequency; f > maxFrequency; f -= 5) {
        //boolean nextFavFound = false;
        if (f < 8785)
        {
            f = 10800;
        }
        for (double f2 : favFrequencies) {
            if (f / 100 == f2) {
                nextFavFound = true;
                //break;
            }
        }
        if (nextFavFound) {
            currentFreq = f /100;
            RadioGUI.lblFreq.setText("FM " + Double.toString(currentFreq)+ "Mhz");
            System.out.println("next favFrequency: " + f / 100);
            nextFavFound = false;
            break;
        }
    }
}

它确实工作得很好，但是当我再次运行该方法时，它将无法使用第一次的新输出值。

Answer 1

使用 for 循环和带小数位的 double 增量时，您会遇到精度问题。解决您的问题的一种实用方法是乘以 100。

public static void main(String[] args) {
    double startFrequency = Math.round(88 * 100);
    double maxFrequency = Math.round(108 * 100);
    for (double f = startFrequency; f < maxFrequency; f += 5) {
        boolean nextFavFound = false;
        for (double f2 : favFrequencies) {
            if (f / 100 == f2) {
                nextFavFound = true;
                break;
            }
        }
        if (nextFavFound) {
            System.out.println("next favFrequency: " + f / 100);
        }
    }
}