java - 为什么我的 double 值中的小数位输出为 ".0"？

Question

这个问题已经有答案了:

Division of integers in Java [duplicate] (7 个回答)

已关闭 8 年前。

我正在网上学习java类(class)，我需要编写一个计算成绩的程序。然而，我的输出应该有小数位，但它有一个 0。我知道当你用一个整数除 double 值时，它会截断(或者删除小数值，以防我错误地使用该词)它，但是我不允许更改初始化或添加任何初始化。这意味着我无法在初始化中将数据类型从 int 更改为 double。

我不太确定正确的术语是什么，因为我在这里和谷歌上的搜索都没有结果。

测试 3 的平均值计算应该有小数位。前两个结果如预期的那样为 97.0 和 88.0。第三个应该是 86.333，三个重复。

 //local variables
 int numTests = 0;       //counts number of tests
 int testGrade = 0;      //individual test grade
 int totalPoints = 0;    //total points for all tests
 double average = 0.0;   //average grade

    //Test 1 Grade
    testGrade = 97;
    numTests++;     //number of tests increased by one.
    totalPoints = totalPoints + testGrade;     //add the test grade to the total points.
    average = (totalPoints / numTests);     //calculate the average out of all the tests.
    System.out.print("n = " + numTests + "  New Test Grade = " + testGrade + "  Total Points = " + totalPoints);
    System.out.println("   Average Score: " + average);   

    //Test 2 Grade
    testGrade = 79;
    numTests++;
    totalPoints += testGrade;
    average = (totalPoints / numTests);
    System.out.print("n = " + numTests + "  New Test Grade = " + testGrade + "  Total Points = " + totalPoints);
    System.out.println("   Average Score: " + average);

    //Test 3 Grade
    testGrade = 83;
    numTests++;
    totalPoints += testGrade;
    average = (totalPoints / numTests);
    System.out.print("n = " + numTests + "  New Test Grade = " + testGrade + "  Total Points = " + totalPoints);
    System.out.println("   Average Score: " + average);

Answer 1

只需将总点数转换为 double，然后除以测试次数即可。

如下所示，

average = ((double) totalPoints / numTests);

或将totalPoints声明为双倍