1）创建部门枚举，对象有：JAVA、HTML、PYTHON 2）创建员工实体类，属性有：姓名、年龄、薪资、部门枚举 3) 实现员工的管理系统(底层数据结构不限)，有添加员工、删除员工、修改员工、查询员工 4）根据姓名、年龄段、薪资、部门等各种情况查询学生 5）编写统计员工信息方法，统计最高工资的员工、最低薪资的员工、根据部门统计员工，通过Stream流统计 用代码实现

1）部门枚举类Department:

public enum Department {
    JAVA,
    HTML,
    PYTHON
}

2）员工实体类Employee:

public class Employee {
    private String name;
    private int age;
    private double salary;
    private Department department;

    // 构造方法、getter和setter方法略

    @Override
    public String toString() {
        return "Employee{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", salary=" + salary +
                ", department=" + department +
                '}';
    }
}

3) 员工管理类EmployeeManagement:

public class EmployeeManagement {
    private List<Employee> employees;

    public EmployeeManagement() {
        employees = new ArrayList<>();
    }

    // 添加员工
    public void addEmployee(Employee employee) {
        employees.add(employee);
    }

    // 删除员工
    public void deleteEmployee(Employee employee) {
        employees.remove(employee);
    }

    // 修改员工
    public void updateEmployee(Employee oldEmployee, Employee newEmployee) {
        int index = employees.indexOf(oldEmployee);
        employees.set(index, newEmployee);
    }

    // 查询员工
    public List<Employee> queryEmployee(Predicate<Employee> predicate) {
        return employees.stream()
                .filter(predicate)
                .collect(Collectors.toList());
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("EmployeeManagement{\n");
        for (Employee employee : employees) {
            sb.append("\t").append(employee).append("\n");
        }
        sb.append("}");
        return sb.toString();
    }
}

4) 查询员工示例：

// 根据姓名查询
List<Employee> employeesByName = employeeManagement.queryEmployee(e -> e.getName().equals("张三"));

// 根据年龄段查询
List<Employee> employeesByAgeRange = employeeManagement.queryEmployee(e -> e.getAge() >= 20 && e.getAge() <= 30);

// 根据薪资查询
List<Employee> employeesBySalary = employeeManagement.queryEmployee(e -> e.getSalary() > 5000);

// 根据部门查询
List<Employee> employeesByDepartment = employeeManagement.queryEmployee(e -> e.getDepartment() == Department.JAVA);

5) 统计员工信息示例：

// 统计最高工资的员工
Optional<Employee> maxSalaryEmployeeOp = employeeManagement.queryEmployee(e -> true)
                .stream()
                .max(Comparator.comparingDouble(Employee::getSalary));
if (maxSalaryEmployeeOp.isPresent()) {
    Employee maxSalaryEmployee = maxSalaryEmployeeOp.get();
    System.out.println("最高工资的员工：" + maxSalaryEmployee);
}

// 统计最低薪资的员工
Optional<Employee> minSalaryEmployeeOp = employeeManagement.queryEmployee(e -> true)
                .stream()
                .min(Comparator.comparingDouble(Employee::getSalary));
if (minSalaryEmployeeOp.isPresent()) {
    Employee minSalaryEmployee = minSalaryEmployeeOp.get();
    System.out.println("最低薪资的员工：" + minSalaryEmployee);
}

// 根据部门统计员工
Map<Department, Long> departmentEmployeeCount = employeeManagement.queryEmployee(e -> true)
                .stream()
                .collect(Collectors.groupingBy(Employee::getDepartment, Collectors.counting()));
System.out.println("各部门员工数量：" + departmentEmployeeCount);

完整代码如下：

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Predicate;
import java.util.stream.Collectors;

public class EmployeeManagement {
    private List<Employee> employees;

    public EmployeeManagement() {
        employees = new ArrayList<>();
    }

    // 添加员工
    public void addEmployee(Employee employee) {
        employees.add(employee);
    }

    // 删除员工
    public void deleteEmployee(Employee employee) {
        employees.remove(employee);
    }

    // 修改员工
    public void updateEmployee(Employee oldEmployee, Employee newEmployee) {
        int index = employees.indexOf(oldEmployee);
        employees.set(index, newEmployee);
    }

    // 查询员工
    public List<Employee> queryEmployee(Predicate<Employee> predicate) {
        return employees.stream()
                .filter(predicate)
                .collect(Collectors.toList());
    }

    // 统计最高工资的员工、最低薪资的员工、根据部门统计员工
    public void statisticsEmployee() {
        // 统计最高工资的员工
        Optional<Employee> maxSalaryEmployeeOp = employeeManagement.queryEmployee(e -> true)
                .stream()
                .max(Comparator.comparingDouble(Employee::getSalary));
        if (maxSalaryEmployeeOp.isPresent()) {
            Employee maxSalaryEmployee = maxSalaryEmployeeOp.get();
            System.out.println("最高工资的员工：" + maxSalaryEmployee);
        }

        // 统计最低薪资的员工
        Optional<Employee> minSalaryEmployeeOp = employeeManagement.queryEmployee(e -> true)
                .stream()
                .min(Comparator.comparingDouble(Employee::getSalary));
        if (minSalaryEmployeeOp.isPresent()) {
            Employee minSalaryEmployee = minSalaryEmployeeOp.get();
            System.out.println("最低薪资的员工：" + minSalaryEmployee);
        }

        // 根据部门统计员工
        Map<Department, Long> departmentEmployeeCount = employeeManagement.queryEmployee(e -> true)
                .stream()
                .collect(Collectors.groupingBy(Employee::getDepartment, Collectors.counting()));
        System.out.println("各部门员工数量：" + departmentEmployeeCount);
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("EmployeeManagement{\n");
        for (Employee employee : employees) {
            sb.append("\t").append(employee).append("\n");
        }
        sb.append("}");
        return sb.toString();
    }

    public static void main(String[] args) {
        EmployeeManagement employeeManagement = new EmployeeManagement();

        // 添加员工
        employeeManagement.addEmployee(new Employee("张三", 25, 6000, Department.JAVA));
        employeeManagement.addEmployee(new Employee("李四", 30, 8000, Department.HTML));
        employeeManagement.addEmployee(new Employee("王五", 20, 5000, Department.JAVA));
        System.out.println(employeeManagement);

        // 删除员工
        Employee employee = new Employee("张三", 25, 6000, Department.JAVA);
        employeeManagement.deleteEmployee(employee);
        System.out.println(employeeManagement);

        // 修改员工
        Employee oldEmployee = new Employee("李四", 30, 8000, Department.HTML);
        Employee newEmployee = new Employee("李四", 30, 9000, Department.PYTHON);
        employeeManagement.updateEmployee(oldEmployee, newEmployee);
        System.out.println(employeeManagement);

        // 查询员工
        List<Employee> employeesByName = employeeManagement.queryEmployee(e -> e.getName().equals("李四"));
        System.out.println("姓名为李四的员工：" + employeesByName);

        List<Employee> employeesByAgeRange = employeeManagement.queryEmployee(e -> e.getAge() >= 20 && e.getAge() <= 30);
        System.out.println("年龄在20~30岁之间的员工：" + employeesByAgeRange);

        List<Employee> employeesBySalary = employeeManagement.queryEmployee(e -> e.getSalary() > 5000);
        System.out.println("薪资大于5000的员工：" + employeesBySalary);

        List<Employee> employeesByDepartment = employeeManagement.queryEmployee(e -> e.getDepartment() == Department.JAVA);
        System.out.println("JAVA部门的员工：" + employeesByDepartment);

        // 统计员工信息
        employeeManagement.statisticsEmployee();
    }
}

enum Department {
    JAVA,
    HTML,
    PYTHON
}

class Employee {
    private String name;
    private int age;
    private double salary;
    private Department department;

    public Employee(String name, int age, double salary, Department department) {
        this.name = name;
        this.age = age;
        this.salary = salary;
        this.department = department;
    }

    // getter和setter方法略

    @Override
    public String toString() {
        return "Employee{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", salary=" + salary +
                ", department=" + department +
                '}';
    }
}