我將如何計算二維數組中的平均值？

Question

首先，我對 Java 並不完全陌生，並且我已經參加過這方面的課程。 最近，一年后我再次拿起它，我對如何計算二維整數數組的平均值有點困惑。 例如，這是一段不包括平均計算的代碼摘錄：

  //Program fills array with x students and their corresponding test grades for n amount of tests

  System.out.println("Amount of students?");
  int numstudents = sc.nextInt();
  System.out.println("Amount of tests?");
  int numtests = sc.nextInt();
  
  int[][] marks  = new int [numstudents][numtests];
  int[] average  = new int [numstudents];
  
  for (int i = 0; i < numstudents; i++) {
     for (int j = 0; j < numtests; j++) {
        System.out.println("Enter the mark for student " + (i+1) + " on test " + (j+1));
        marks[i][j] = sc.nextInt();
        //Array is filled with grades. 
     }
  }

現在假設我想計算每個學生的平均值並將值存儲在average[]數組中。 我的主要問題是弄清楚如何循環它，以便它包含對marks[0][j]的每個測試，然后轉到marks[1][j]等等。 如果我執行以下代碼之類的操作，它將獲取每個測試值並將其除以numtests 。

 for (int i = 0; i < numstudents; i++) {
     for (int j = 0; j < numtests; j++) {
        average[i] = marks[i][j]/numtests;
        System.out.println("The average is " + average[i]);
     }
  }

Answer 1

我認為應該計算平均[i]

    for (int i = 0; i < numstudents; i++) {
        //here
        for (int j = 0; j < numtests; j++) {
        }

編寫如下代碼怎么樣？

    int eachsum = 0;
    for (int i = 0; i < numstudents; i++) {
        for (int j = 0; j < numtests; j++) {
             eachsum += marks[i][j];
        }
        average[i] = eachsum/numtests;
        System.out.println("The average for student " + (i+1) + " is " + average[i]);
        eachsum = 0;
    }

Answer 2

您可以執行以下操作：

int[] average = Arrays.stream(marks)
        .map(ints -> Arrays.stream(ints).summaryStatistics().getAverage())
        .mapToLong(Math::round)
        .mapToInt(Math::toIntExact)
        .toArray();

---

輸入：

    int[][] marks = {
            {80, 70 ,90},
            {90, 65 ,90},
            {50, 70 ,70},
            {80, 75 ,85}
    };

Output：

[80,
 82,
 63,
 80]