java idex 创建学校类和几个班级类，再创建几个学生类，计算出全校有多少名同学。

//学校类 class School { //多个班级 private Class[] aClass; private String schoolName; public void School() { } public Class[] getaClass() { return aClass; } public void setaClass(Class[] aClass) { this.aClass = aClass; } public String getSchoolName() { return schoolName; } public void setSchoolName(String schoolName) { this.schoolName = schoolName; } } //班级类 class Class { //多个学生 private Student[] student; private String aClassName; public void Class() { } public Student[] getStudent() { return student; } public void setStudent(Student[] student) { this.student = student; } public String getaClassName() { return aClassName; } public void setaClassName(String aClassName) { this.aClassName = aClassName; } } //学生类 class Student { private String name; private int age; public void Student() { } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } } //测试类 public class Test { public static void main(String[] args) { School school=new School(); school.setaClass(new Class[10]); for (int i=0;i<10;i++){ school.getaClass()[i]=new Class(); school.getaClass()[i].setStudent(new Student[30]); school.getaClass()[i].setaClassName("班级"+i); for (int j=0;j<30;j++){ school.getaClass()[i].getStudent()[j]=new Student(); school.getaClass()[i].getStudent()[j].setAge(j+10); school.getaClass()[i].getStudent()[j].setName("学生"+j); } } for (int i=0;i<10;i++){ for (int j=0;j<30;j++){ System.out.println("班级："+school.getaClass()[i].getaClassName()+" 名字："+school.getaClass()[i].getStudent()[j].getName()+" 年龄"+school.getaClass()[i].getStudent()[j].getAge()); } } } }

package school;

public class CalcStudent {

	public static void main(String[] args) {
		School school = new School("北京大学");
		Clazz cla1 = new Clazz(202101,"金融202101班",school);
		Clazz cla2 = new Clazz(202102,"金融202102班",school);
		Student s1 = new Student(1001, "张三", "男", 21, cla1);
		Student s2 = new Student(1002, "丽丽", "女", 20, cla1);
		Student s3 = new Student(1003, "李四", "男", 22, cla2);
		Student s4 = new Student(1004, "黄蓉", "女", 19, cla2);
		
		System.out.println(s1);
		System.out.println(s2);
		System.out.println(s3);
		System.out.println(s4);
		System.out.println("全校共有"+Student.count+"人.");
		
	}

}
class School{
	String schoolName;
	public School() {}
	public School(String schoolName) {
		this.schoolName = schoolName;
	}
	@Override
	public String toString() {
		
		return "学校名称是："+this.schoolName;
	}
}
class Clazz{
	int classId;
	String className;
	School school;
	public Clazz() {}
	public Clazz(int classId,String className,School school) {
		this.classId = classId;
		this.className = className;
		this.school = school;
	}
	@Override
	public String toString() {
		
		return "班级名称是："+this.className+",学校:" + school.schoolName;
	}
}
class Student{
	int studId;
	String studName;
	String sex;
	int age;
	Clazz cls;
	static int count;
	public Student() {
		count++;
	}
	public Student(int studId,String studName,String sex,int age,Clazz cls) {
		this.studId = studId;
		this.studName = studName;
		this.sex = sex;
		this.age = age;
		this.cls = cls;
		count++;
	}
	@Override
	public String toString() {
		
		return "学号："+this.studId+",姓名:"+this.studName +",班级:"+cls.className +",学校"+cls.school.schoolName;
	}
}

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