如何使用Java中另一个类的变量

Question

Please help me how can I use a variable from deviation_2DArray.java into NBC.java , in NBC.java I want to average b[i] by d[i][j] and c[j]

Example:

b[1]=avg (d[1][1]+d[1][2]+.....+d[1][5])

Thanks in advance.

2DArray.java

public class 2DArray {

    public static void main(String[] args) {

        double[][] d = new double[6][4];

        double[][] e = {
            {}, {
                0.0, 0.6, 0.0, 0.0
            }, {
                0.0, 0.2, 0.5, 0.1
            }, {
                0.0, 0.2, 0.5, 0.4
            }, {
                0.0, 0.2, 0.5, 0.7
            }, {
                0.0, 0.0, 0.0, 0.9
            }
        };

        double[] avg = new double[4];
        double[] sum = new double[4];
        int i, j, k;

        //average of column
        for (j = 1; j < e[1].length; j++) {
            for (i = 1; i < e.length; i++)
            System.out.println("e[" + i + "][" + j + "] = " + e[i][j]);
        }

        for (j = 1; j < e[1].length; j++) {

            sum[j] = 0.0;
            k = 0;
            for (i = 1; i < e.length; i++)

            if (e[i][j] > 0.0) {
                sum[j] += e[i][j];
                k++;
            }
            avg[j] = sum[j] / k;

            System.out.println("Average of j[" + j + "] = " + avg[j]);

        }

        for (j = 1; j < e[1].length; j++) {
            for (i = 1; i < e.length; i++)

            if (e[i][j] > 0.0) {

                d[i][j] = Math.abs(e[i][j] - avg[j]);
                System.out.println("d[" + i + "][" + j + "] = " + d[i][j]);

            }
        }

    }
}

NBC.java

public class NBC {
    public static void main(String[] args) {

        double[] b = new double[6];
        double[] c = new double[4];
        int count;

        b[i] = d[i][j] / count;
    }

}

Answer 1

我将它恢复为一个简单的词： getters 。

Answer 2

You need to create class-level fields in the 2DArray class and provide getter methods to those fields. Then NBC would need to have an instance of 2DArray unless you made those fields / getters static.

Currently your d variable in 2DArray is only in the scope of the main method, therefore just providing a getter won't solve the problem because d only has scope in the method.

Also, each class has its own main method. You can only execute one main per application. So how is your flow of control getting from 2DArray to NBC ? If 2DArray is calling NBC , then you could pass the array as an argument.

Answer 3

Create a method in the 2DArray something like this:

public double getElement(int i, int j) {
  return d[i][j];
}