Question

编辑：我已在该计划的输出中进行了编辑。

该程序要求估计给定的值mu。用户给出mu值，并提供四个不等于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的值为238,900，w = 14，x = 102329，y = 1936，z = 13 则估计值应为239,103，误差约为0.08％。

我的代码与for循环完美无缺：

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%

然而，使用while循环，我无法复制它。

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){
}

类似地对使用变量c＆amp;的while循环执行此操作。 d。

Answer 2

Daniel's answer is correct： while循环的结构应为：

    int a=0, b=0, c=0, d=0;
    while (a < length) {

        b=0;
        while (b < length) {
            c=0;
            while (c < length) {
                d=0;
                while (d < length) {
                    d++;
                }
                c++;
            }
            b++;
        }
        a++;
    }

程序适用于for循环但不适用于while循环？

2 个答案: