Java循环3个班级，再循环录入该班级的5个学生的序号和成绩，录入学号时判断长度，录入分值时判断是否为负数，录入完一个班级后打印出该班级平均分和及格人数，当全部录入完毕后计算平均分和及格人数并显示

在Java中，我们可以创建一个更复杂的数据结构，比如二维数组或列表来处理这种需求。以下是一个示例，使用嵌套循环来实现：

import java.util.ArrayList;
import java.util.Scanner;

class Student {
    String id;
    double score;

    Student(String id, double score) {
        this.id = id;
        if (id.length() > 0) {
            this.score = score;
        } else {
            throw new IllegalArgumentException("学号不能为空");
        }
        if (score < 0) {
            throw new IllegalArgumentException("成绩不能为负数");
        }
    }
}

public class ClassGrade {
    private ArrayList<ArrayList<Student>> classes;
    private double overallAverage = 0;
    private int totalPasses = 0;

    public ClassGrade(int numClasses, int studentsPerClass) {
        classes = new ArrayList<>();
        for (int i = 1; i <= numClasses; i++) {
            ArrayList<Student> classStudents = new ArrayList<>();
            for (int j = 1; j <= studentsPerClass; j++) {
                Scanner scanner = new Scanner(System.in);
                System.out.println("请输入第 " + i + " 班第 " + j + " 学生的学号:");
                String id = scanner.next();
                if (id.isEmpty()) {
                    throw new IllegalArgumentException("学号不能为空");
                }
                System.out.println("请输入第 " + i + " 班第 " + j + " 学生的成绩:");
                double score = scanner.nextDouble();
                if (score < 0) {
                    throw new IllegalArgumentException("成绩不能为负数");
                }
                classStudents.add(new Student(id, score));
                scanner.close();
            }
            classes.add(classStudents);
            printClassInfo(i, classStudents);
        }
        calculateOverallAverage();
    }

    private void printClassInfo(int className, ArrayList<Student> classStudents) {
        double classAverage = calculateClassAverage(classStudents);
        int passes = countPasses(classStudents);

        System.out.println("班级 " + className + " 平均分: " + classAverage);
        System.out.println("班级 " + className + " 及格人数: " + passes);
        overallAverage += classAverage;
        totalPasses += passes;
    }

    private double calculateClassAverage(ArrayList<Student> classStudents) {
        double sum = 0;
        for (Student student : classStudents) {
            sum += student.score;
        }
        return sum / classStudents.size();
    }

    private int countPasses(ArrayList<Student> classStudents) {
        int passes = 0;
        for (Student student : classStudents) {
            if (student.score >= 60) {
                passes++;
            }
        }
        return passes;
    }

    public void calculateOverallAverage() {
        if (totalStudents() > 0) {
            overallAverage /= totalStudents();
        }
        System.out.println("所有班级的平均分: " + overallAverage);
        System.out.println("总及格人数: " + totalPasses);
    }

    private int totalStudents() {
        int total = 0;
        for (ArrayList<Student> classStudents : classes) {
            total += classStudents.size();
        }
        return total;
    }

    public static void main(String[] args) {
        int numClasses = 3;
        int studentsPerClass = 5;
        ClassGrade grade = new ClassGrade(numClasses, studentsPerClass);
    }
}

这个代码会按班录入学生的学号和成绩，每次录入完成后会打印出班级信息，包括平均分和及格人数。录入完毕后，会计算整体的平均分和总及格人数。