java题目，大神帮忙。

员工属性加上部门id，sql语句左连接查部门id再设置条件，平均年龄等都可以查出来

// Demo6.java
package com.demo6;

import java.util.Date;

public class Demo6 {

	public static void main(String[] args) {
		
		Department department = new Department();
		department.setName("研发部");
		
		// 添加员工
		Employee emp1 = new Employee();
		emp1.setName("张三");
		emp1.setGender("男");
		emp1.setPhone("123456789");
		emp1.setBirthday(new Date(1980, 5, 6));
		department.addEmployee(emp1);
		
		Employee emp2 = new Employee();
		emp2.setName("李四");
		emp2.setGender("女");
		emp2.setPhone("123856989");
		emp2.setBirthday(new Date(1985, 5, 6));
		department.addEmployee(emp2);
		
		Employee emp3 = new Employee();
		emp3.setName("王五");
		emp3.setGender("男");
		emp3.setPhone("333456789");
		emp3.setBirthday(new Date(1989, 5, 6));
		department.addEmployee(emp3);
		
		// 删除名为张三的员工
		department.removeEmployee("张三");
		
		System.out.println("员工人数：" + department.getEmployees().size());
		
		// 统计某部门男女性别分别是多少 
		
		int male = 0, female = 0;
		
		for(Employee emp : department.getEmployees()) {
			if(emp.getGender() == "男") {
				male++;
			} else if (emp.getGender() == "女") {
				female++;
			}
		}
		
		System.out.println("男：" + male + "，女：" + female);
		
		// 获取员工平均年龄
		int average = department.getAverageAge();
		System.out.println("平均年龄：" + average);
		
		// 获取年龄最的员工
		Employee emp = department.getMaxAgeEmployee();
		System.out.println(emp != null ? "年龄最大的员工：" + emp.getName() : "没有员工。");
	}

}

// Employee.java
package com.demo6;

import java.util.Calendar;
import java.util.Date;

public class Employee {

	private String name;

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

	// 性别
	private String gender;

	public String getGender() {
		return this.gender;
	}

	public void setGender(String gender) {
		this.gender = gender;
	}

	// 电话
	private String phone;

	public String getPhone() {
		return this.phone;
	}

	public void setPhone(String phone) {
		this.phone = phone;
	}

	// 出生日期
	private Date birthday;

	public Date getBirthday() {
		return this.birthday;
	}

	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	
	// 获取年龄
	@SuppressWarnings("deprecation")
	public int getAge() {
		return Calendar.getInstance().get(Calendar.YEAR) - this.birthday.getYear();
	}

}

// Department.java
package com.demo6;

import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;

/**
 *	部门类
 */
public class Department {

	private String name;

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

	private List employees = new ArrayList();

	public List getEmployees() {
		return this.employees;
	}

	// 添加员工
	public void addEmployee(Employee employee) {
		if (employee != null) {
			this.employees.add(employee);
		}
	}
	
	// 删除员工
	public void removeEmployee(String name) {
		
		Employee employee = null;
		
		for(Employee emp : employees) {
			if(emp.getName() == name) {
				employee = emp;
			}
		}
		
		employees.remove(employee);
	}
	
	// 获取工员平均年龄
	@SuppressWarnings("deprecation")
	public int getAverageAge() {
		
		int total = 0;
		
		for(Employee emp : employees) {
			total += emp.getAge();
		}
		
		return total / this.employees.size();
	}
	
	// 获取年龄最大的员工
	public Employee getMaxAgeEmployee() {
		
		Employee employee = null;
		
		for(Employee emp : employees) {
			if(employee == null) {
				employee = emp;
			} else if (employee.getAge() < emp.getAge()) {
				employee = emp;
			}
		}
		
		return employee;
	}

}