我假设每一行都有一个学生的分数。如果是这样，就不需要嵌套循环来计算特定学生的平均值。请参见下面代码中的注解。

public static void main(String[] args) {
        String[] classNames = {"Rick", "Tom", "Jill", "Megan"};
        double[][] classResults = {
                {100.0, 87.5, 95.3, 80.0},
                {95.6, 25.0, 70.7, 85.0},
                {95.3, 96.7, 82.6, 87.5},
                {61.8, 55.9, 60.1, 60.6}
        };

        System.out.println("Class results: ");
        processResults(classNames, classResults);
    }

    public static void processResults(String[] names, double[][] scores) {
        for (int i = 0; i < names.length; i++) {
            System.out.println("Student: " + names[i]);
            System.out.print("\tAverage: ");
            //A 2D array is an array of arrays - so here, we use the 1D array containing the scores for the current student based on the counter.
            System.out.println(returnAverage(scores[i]) + "\t");
        }
    }

    public static double returnAverage(double scores[]) {
        double sum = 0;

        //Add all the scores for this student - no need for a nested loop if you only process data for one student.
        for (int j = 0; j < scores.length; j++) {
            sum += scores[j];
        }

        //Calculate the average for this student.
        double average = sum/scores.length;
        return average;
    }

如果我理解正确的话，你需要整个二维阵列的平均值，对吗？所以，你需要把总数除以总计数。更多解释请参见注解。

public static double returnAverage (double scores[][]) {
    double sum = 0; // This should be initialized once.
    int count = 0; // This should also be initialized once, before the computation.
    for (int l = 0; l < scores.length; l++) {
        for (int j = 0; j < scores[l].length; j++) {
            sum += scores[l][j];
            count++;
        }
    }
    return sum / count; // Compute the result at the end.
}