java - 对数组使用 if 语句

Question

在注释步骤4我试图将当前数组元素添加到sum中，将当前数组元素与max_test进行比较，如果它更大，则将其保存在变量max_test中。并将当前元素与 min_test 进行比较，如果较小，则将其保存在 min_test 中。但是我不断收到错误

Grades5.java:55: error: bad operand types for binary operator '>'
        if (grades[r] > grades[max_test]) 
                      ^
  first type:  int[]
  second type: int[]

Grades5.java:57: error: bad operand types for binary operator '<'
        if (grades[r] < grades[min_test])
                      ^
  first type:  int[]
  second type: int[]

Grades5.java:59: error: bad operand types for binary operator '+'
           sum += grades[r];
               ^
  first type:  int
  second type: int[]

3 errors

代码:

 import java.util.Scanner;

public class Grades5
{
  public static void main(String[] args)
  {
int[][] grades = {
                   { 87,  96, 100},
                   { 68,  75,  72},
                   { 99, 100,  95},
                   {100,  96,  70},
                   { 75,  60,  79},
                 };
int how_many_grades = grades.length * grades[0].length;

// -----------------
// Output the grades
// -----------------
System.out.print("           ");
for (int i = 0; i < grades[0].length; i++)
  System.out.print("Test " + (i + 1) + "  ");
System.out.println("Average");
for (int r = 0; r < grades.length; r++)
{
  int sum = 0;  // Sum of one student's tests

  // -------------------
  // Process one student
  // -------------------
  System.out.print("Student " + (r + 1) + "  ");
  for (int c = 0; c < grades[r].length; c++)
  {
    System.out.printf("%6d  ", grades[r]);                                                        // Step 1
      //sum += grades[c];                                                                     // Step 2
  }
  System.out.printf("%7.2f\n", (double)sum / grades[r].length);
}

// ----------------
// Output a summary
// ----------------
int max_test,  // Maximum test score
    min_test,  // Minimum test score
    sum = 0;   // Sum of all student tests

max_test = min_test = grades[0][0];    // Step 3
for (int r = 0; r < grades.length; r++)
{
  // -------------------
  // Process one student
  // -------------------
  for (int c = 0; c < grades[r].length; c++)
  {
                                     // Step 4
    if (grades[r] > grades[max_test]) 
      max_test = c; 
    if (grades[r] < grades[min_test])
       min_test = c;
       sum += grades[r];
  }
}
System.out.println("Highest test score: " + max_test);
System.out.println("Lowest  test score: " + min_test);
System.out.printf("Average test score: %.1f\n",
                  (double)sum / how_many_grades);
  }
}

Answer 1

您的问题是 grades[r] 不是整数。它是整数的数组。你必须处理两个索引

sum += grades[i][j];

为了摆脱编译错误。

其他错误似乎是一样的。大体上可以这样想象:

grades[1] -> { 87,  96, 100}
grades[2] -> { 68,  75,  72}

和

grades[1][1] -> 87;
grades[1][2] -> 96;

等..