java - 尝试查找数组平均值时数组大小不正确，如何解决此问题？

Question

在我的类(class)中，我有多个科目，每个科目可以有很多作业。我试图找到“taskingGradeAchieved”不为空的每项作业的平均成绩。

在一个数组中，我存储了这些 assignmentGradeAchieved。我想找到平均结果(将每个数字加在一起然后除以项目数)但是它没有显示正确的数组大小。当它应该是 2 时却显示为 1。这是我尝试查找数组大小的代码行: arraySize = (assignmentGradesAchieved.size());

//对于属于主题的每个作业，如果AssignmentGradeAchieved 不为null，则将AssignmentGradeAchieved 添加到名为AssignmentGradesAchieved 的数组列表中。//如果一个科目有多个具有AssignmentGradeAchieved 的作业，则应将多个AssignmentGradeAchieved 添加到名为AssignmentGradesAchieved 的arryalist 中。因此数组的大小应该大于一。//我的一个科目有两项作业，两者的成绩均为AssignmentGradeAchieved，因此数组大小应为2而不是1

    for(int i=0; i<subjects.size(); i++){ //for each subject in the list
        Subject subject = subjects.get(i);


        List<Assignment> assignments = subject.getAssignment(); //Get the list of assignments belonging to current subject

            for(int y=0; y<assignments.size(); y++ ) { //For each assignment in the list 
                Assignment assignment = assignments.get(y);

                ArrayList<Double> assignmentGradesAchieved = new ArrayList<Double>(); 
                if(assignments.get(y).getAssignmentGradeAchieved()!=null) {
                    assignmentGradesAchieved.add(assignments.get(y).getAssignmentGradeAchieved());
                    arraySize = 0;
                    arraySize = (assignmentGradesAchieved.size());  
                    for(int z=0; z<assignmentGradesAchieved.size(); z++) {
                        arraySize = 0;
                        allAssignments = allAssignments + assignmentGradesAchieved.get(z);

                        arraySize = (assignmentGradesAchieved.size());      
                        averageAssignGrade = (allAssignments / arraySize);

                    }
                }
    }


    }

解决方案:

   for(int i=0; i<subjects.size(); i++){ //for each subject in the list
        Subject subject = subjects.get(i);

        List<Assignment> assignments = subject.getAssignment(); //Get the list of assignments belonging to current subject
        ArrayList<Double> assignmentGradesAchieved = new ArrayList<Double>(); 

            for(int y=0; y<assignments.size(); y++ ) { //For each assignment in the list 
                Assignment assignment = assignments.get(y);
                allAssignments =0;

                if(assignments.get(y).getAssignmentGradeAchieved()!=null) {
                    assignmentGradesAchieved.add(assignments.get(y).getAssignmentGradeAchieved());

                for(int z=0; z<assignmentGradesAchieved.size(); z++) {

                    allAssignments = allAssignments + assignmentGradesAchieved.get(z);
                }
                }

    }
            arraySize = 0;
            arraySize = (assignmentGradesAchieved.size());  
            averageAssignGrade = (allAssignments / arraySize);


    }

Answer 1

您的 assignmentGradesAchieved 声明位于 for 循环内，因此它总是会被重置，因此您的变量将始终只有一个作业等级。将您的声明置于循环之外