AP计算机科学A

public static double averageOfPositives(int[] arr) {
    int sum = 0;
    int count = 0;

    for (int num : arr) {
        if (num > 0) {
            sum += num;
            count++;
        }
    }

    if (count == 0) {
        return 0.0;
    }

    return (double) sum / count;
}

public static int countVowels(String str) {
    int count = 0;
    String vowels = "aeiouAEIOU";

    for (int i = 0; i < str.length(); i++) {
        char c = str.charAt(i);
        if (vowels.indexOf(c) != -1) {
            count++;
        }
    }

    return count;
}

import java.util.ArrayList;

public class Student {
    private String name;
    private int id;
    private ArrayList<Double> grades;

    public Student(String name, int id) {
        this.name = name;
        this.id = id;
        this.grades = new ArrayList<>();
    }

    public void addGrade(double grade) {
        grades.add(grade);
    }

    public double getAverage() {
        if (grades.isEmpty()) {
            return 0.0;
        }

        double sum = 0.0;
        for (double grade : grades) {
            sum += grade;
        }

        return sum / grades.size();
    }

    public String toString() {
        return "Student[name=" + name + ", id=" + id + ", average=" + getAverage() + "]";
    }
}