Question

java定义一个学校的职工类

抽象出教师、学生和后勤人员的公共特性和方法，使用继承定义教师、学生和后勤人员等新类，每个类都又区别于其他类的特殊属性，构造对应的方法分别计算出教师、学生和后勤人员的人数，计算教师、学生和后勤人员的平均年龄

Answer 1

import java.util.*;

public class Test1
{

public static void main(String[] args)
{
Student s1 = new Student(15);
Student s2 = new Student(12);
Student s3 = new Student(15);
Student s4 = new Student(13);
Student s5 = new Student(11);
Teacher t1 = new Teacher(35);
Teacher t2 = new Teacher(30);
Worker w1 = new Worker(45);
Worker w2 = new Worker(43);
Worker w3 = new Worker(42);
List<People> students = new ArrayList<People>();
List<People> teachers = new ArrayList<People>();
List<People> workers = new ArrayList<People>();
students.add(s1);
students.add(s2);
students.add(s3);
students.add(s4);
students.add(s5);
teachers.add(t1);
teachers.add(t2);
workers.add(w1);
workers.add(w2);
workers.add(w3);
Test1 t = new Test1();
s1.sayHello();
t.display(students);
t1.sayHello();
t.display(teachers);
w1.sayHello();
t.display(workers);
}

public void display(List<People> as)
{
int Count = 0;
int sum = 0;
for(People p:as)
{
sum = sum + p.age;
Count++;
}
System.out.println("共有人数" + Count);
System.out.println("平均年龄" + (sum/Count));
}
}

abstract class People
{
int age; //年龄
public People(int age)
{
this.age = age;
}
public abstract void sayHello();
public void displayAvgAge()
{
System.out.println("年龄:" + age);
}
}

class Student extends People
{
public Student(int age)
{
super(age);//调用抽象类的构造方法构造
}
public void sayHello()
{
System.out.println("I'm a student!");
}
}

class Teacher extends People
{
public Teacher(int age)
{
super(age);//调用抽象类的构造方法构造
}
public void sayHello()
{
System.out.println("I'm a teacher!");
}
}

class Worker extends People
{
public Worker(int age)
{
super(age);//调用抽象类的构造方法构造
}
public void sayHello()
{
System.out.println("I'm a worker!");
}
}

总结一下，主要就是写了一个abstract类，里面有个abstract方法。当学生老师职工分别实现的时候要重写这个方法。然后算那个平均年龄的叫我十分匪夷所思。加到类里面不合适，先用ArrayList（集合框架，灰常好用）来搞一个吧。运行完全正常。楼主建立一个Test1.java文件，然后编译一下，用虚拟机跑一下就可以看见结果。
共同的属性就是age，共同的方法就是getAvgAge（）,每个类特殊的方法就是sayHello();