java - 程序适用于 for 循环，但不适用于 while 循环？

Question

编辑:我已经在程序的输出中进行了编辑。

该程序要求估计给定值 mu。用户给出一个值 mu，同时还提供了四个不等于 1 的不同数字(称为 w、x、y、z)。然后，程序尝试使用 de Jaeger 公式找到 mu 值的估计值。

如果我输入 mu 值 238,900，并且 w=14、x=102329、y=1936、z=13那么估计值应该是239,103，误差约为0.08%。

我的 for 循环代码工作得很好:

public static void main(String[] args) {
    SimpleReader in = new SimpleReader1L();
    SimpleWriter out = new SimpleWriter1L();

    double bestEstimate = 0; // used to hold the estimate the computer while return

    double bestA = 0, bestB = 0, bestC = 0, bestD = 0; // to hold the values of the exponents for each number

    double[] exponents = { -5, -4, -3, -2, -1, -1.0 / 2.0, -1.0 / 3.0,
            -1.0 / 4.0, 0, 1.0 / 4.0, 1.0 / 3.0, 1.0 / 2.0, 1, 2, 3, 4, 5 };
    double[] userNumbers = new double[4];

    double mu = getPositiveDouble(in, out);

    for (int i = 0; i < 4; i++) {
        userNumbers[i] = getPositiveDoubleNotOne(in, out);
    }

    for (int a = 0; a < exponents.length; a++) {
        double a1 = Math.pow(userNumbers[0], exponents[a]);
        for (int b = 0; b < exponents.length; b++) {
            double b1 = Math.pow(userNumbers[1], exponents[b]);
            for (int c = 0; c < exponents.length; c++) {
                double c1 = Math.pow(userNumbers[2], exponents[c]);
                for (int d = 0; d < exponents.length; d++) {
                    double d1 = Math.pow(userNumbers[3], exponents[d]);

                    double currentEstimate = a1 * b1 * c1 * d1;
                    if (Math.abs(mu - currentEstimate) < Math
                            .abs(mu - bestEstimate)) {
                        bestEstimate = currentEstimate;
                        bestA = exponents[a];
                        bestB = exponents[b];
                        bestC = exponents[c];
                        bestD = exponents[d];
                    }
                }
            }
        }

    }

    out.println("Best estimate: " + bestEstimate);
    out.println(userNumbers[0] + "^" + bestA + ", " + userNumbers[1] + "^"
            + bestB + ", " + userNumbers[2] + "^" + bestC + ", "
            + userNumbers[3] + "^" + bestD);
    out.println("Error: " + calculateError(mu, bestEstimate) * 100 + "%");

}

输出:

 Enter a positive real number: 238900
 Enter a positive real number that isn't 1: 14
 Enter a positive real number that isn't 1: 102329
 Enter a positive real number that isn't 1: 1936
 Enter a positive real number that isn't 1: 13
 Best estimate: 239102.78648033558
 14.0^-5.0, 102329.0^1.0, 1936.0^0.5, 13.0^4.0
 Error: 0.08488341579555334%

但是，使用 while 循环，我无法复制此内容。

while (a < exponents.length) {
        double a1 = Math.pow(userNumbers[0], exponents[a]);
        while (b < exponents.length) {
            double b1 = Math.pow(userNumbers[1], exponents[b]);
            while (c < exponents.length) {
                double c1 = Math.pow(userNumbers[2], exponents[c]);
                while (d < exponents.length) {
                    double d1 = Math.pow(userNumbers[3], exponents[d]);
                    double currentEstimate = a1 * b1 * c1 * d1;
                    if (Math.abs(mu - currentEstimate) < Math
                            .abs(mu - bestEstimate)) {
                        bestEstimate = currentEstimate;
                        bestA = exponents[a];
                        bestB = exponents[b];
                        bestC = exponents[c];
                        bestD = exponents[d];

                    }
                    d++;

                }
                c++;

            }
            b++;

        }
        a++;

    }

输出:

Enter a positive real number: 238900
Enter a positive real number that isn't 1: 14
Enter a positive real number that isn't 1: 102329
Enter a positive real number that isn't 1: 1936
Enter a positive real number that isn't 1: 13
Best estimate: 0.0
14.0^0.0, 102329.0^0.0, 1936.0^0.0, 13.0^0.0

Answer 1

您尚未初始化接下来几次迭代的变量。

您需要在各自的 while 循环之外重新初始化用于 while 循环条件检查的变量。即

b = 0;
while(b < exponents.length){
}

对使用变量 c 和 d 的 while 循环执行类似的操作。