(1)针对实验4编写的Staff类，分别编写NameComparator，AgeComparator和ComplexComparator比较器。其中ComplexComparator为复合比较器，至少选用两个关键字来排序，关键字选择、次序及升降序均由同学们自行设计。 (2)编写一个测试类，在测试类中添加若干个Staff, Teacher, SecurityGuard, Dean实例(个数及内容自定)，并在测试类中定义并测试如下方法：①编写一个方法private static void printName(Staff[] staffs)打印出每个人的名字；②编写一个方法private static void printSalary(Staff[] staffs)打印出Staff类或者其子类对象的薪水(注意：Staff的薪水只有salary，Teacher的薪水为salary+postAllowance，SecurityGuard的薪水为salary+dangerousAllowance，而Dean的薪水则为salary+postAllowance+adminAward)；③编写一方法private static void sortBySalary(Staff[] staffs)，支持对Staff类及其子类按照各自的薪水降序排序；④编写一方法private static void sortByAge(Staff[] staffs)，对Staff对象按照年龄升序排序，再编写一个方法按name升序进行排序；⑤编写一方法sortByDateHired，支持对Staff类及其子类按照各自的dateHired升序排序，可以使用java.util.Date类的getTime方法。

以下是代码实现：

Staff.java

import java.util.Date;

public class Staff {
    private String name;
    private int age;
    private Date dateHired;
    private double salary;

    public Staff(String name, int age, Date dateHired, double salary) {
        this.name = name;
        this.age = age;
        this.dateHired = dateHired;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public Date getDateHired() {
        return dateHired;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

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

Teacher.java

import java.util.Date;

public class Teacher extends Staff {
    private double postAllowance;

    public Teacher(String name, int age, Date dateHired, double salary, double postAllowance) {
        super(name, age, dateHired, salary);
        this.postAllowance = postAllowance;
    }

    public double getPostAllowance() {
        return postAllowance;
    }

    public void setPostAllowance(double postAllowance) {
        this.postAllowance = postAllowance;
    }

    @Override
    public double getSalary() {
        return super.getSalary() + postAllowance;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "name='" + getName() + '\'' +
                ", age=" + getAge() +
                ", dateHired=" + getDateHired() +
                ", salary=" + getSalary() +
                '}';
    }
}

SecurityGuard.java

import java.util.Date;

public class SecurityGuard extends Staff {
    private double dangerousAllowance;

    public SecurityGuard(String name, int age, Date dateHired, double salary, double dangerousAllowance) {
        super(name, age, dateHired, salary);
        this.dangerousAllowance = dangerousAllowance;
    }

    public double getDangerousAllowance() {
        return dangerousAllowance;
    }

    public void setDangerousAllowance(double dangerousAllowance) {
        this.dangerousAllowance = dangerousAllowance;
    }

    @Override
    public double getSalary() {
        return super.getSalary() + dangerousAllowance;
    }

    @Override
    public String toString() {
        return "SecurityGuard{" +
                "name='" + getName() + '\'' +
                ", age=" + getAge() +
                ", dateHired=" + getDateHired() +
                ", salary=" + getSalary() +
                '}';
    }
}

Dean.java

import java.util.Date;

public class Dean extends Teacher {
    private double adminAward;

    public Dean(String name, int age, Date dateHired, double salary, double postAllowance, double adminAward) {
        super(name, age, dateHired, salary, postAllowance);
        this.adminAward = adminAward;
    }

    public double getAdminAward() {
        return adminAward;
    }

    public void setAdminAward(double adminAward) {
        this.adminAward = adminAward;
    }

    @Override
    public double getSalary() {
        return super.getSalary() + adminAward;
    }

    @Override
    public String toString() {
        return "Dean{" +
                "name='" + getName() + '\'' +
                ", age=" + getAge() +
                ", dateHired=" + getDateHired() +
                ", salary=" + getSalary() +
                '}';
    }
}

NameComparator.java

import java.util.Comparator;

public class NameComparator implements Comparator<Staff> {
    @Override
    public int compare(Staff o1, Staff o2) {
        return o1.getName().compareTo(o2.getName());
    }
}

AgeComparator.java

import java.util.Comparator;

public class AgeComparator implements Comparator<Staff> {
    @Override
    public int compare(Staff o1, Staff o2) {
        return Integer.compare(o1.getAge(), o2.getAge());
    }
}

ComplexComparator.java

import java.util.Comparator;

public class ComplexComparator implements Comparator<Staff> {
    @Override
    public int compare(Staff o1, Staff o2) {
        if (o1.getSalary() == o2.getSalary()) {
            return o1.getDateHired().compareTo(o2.getDateHired());
        } else {
            return Double.compare(o2.getSalary(), o1.getSalary());
        }
    }
}

TestStaff.java

import java.util.Arrays;
import java.util.Date;

public class TestStaff {
    public static void main(String[] args) {
        Staff[] staffs = {
                new Staff("Jack", 25, new Date(), 5000),
                new Teacher("Tom", 35, new Date(), 8000, 2000),
                new SecurityGuard("Jerry", 40, new Date(), 6000, 1000),
                new Dean("Rose", 45, new Date(), 10000, 3000, 4000)
        };

        // 打印每个人的名字
        printName(staffs);

        // 打印出Staff类或者其子类对象的薪水
        printSalary(staffs);

        // 按照各自的薪水降序排序
        sortBySalary(staffs);
        System.out.println("按照各自的薪水降序排序:");
        for (Staff staff : staffs) {
            System.out.println(staff);
        }

        // 对Staff对象按照年龄升序排序，再按照name升序进行排序
        sortByAge(staffs);
        System.out.println("对Staff对象按照年龄升序排序，再按照name升序进行排序:");
        for (Staff staff : staffs) {
            System.out.println(staff);
        }

        // 对Staff类及其子类按照各自的dateHired升序排序
        sortByDateHired(staffs);
        System.out.println("对Staff类及其子类按照各自的dateHired升序排序:");
        for (Staff staff : staffs) {
            System.out.println(staff);
        }
    }

    private static void printName(Staff[] staffs) {
        System.out.println("每个人的名字:");
        for (Staff staff : staffs) {
            System.out.println(staff.getName());
        }
        System.out.println();
    }

    private static void printSalary(Staff[] staffs) {
        System.out.println("Staff类或者其子类对象的薪水:");
        for (Staff staff : staffs) {
            System.out.println(staff.getSalary());
        }
        System.out.println();
    }

    private static void sortBySalary(Staff[] staffs) {
        Arrays.sort(staffs, new Comparator<Staff>() {
            @Override
            public int compare(Staff o1, Staff o2) {
                return Double.compare(o2.getSalary(), o1.getSalary());
            }
        });
    }

    private static void sortByAge(Staff[] staffs) {
        Arrays.sort(staffs, new AgeComparator().thenComparing(new NameComparator()));
    }

    private static void sortByDateHired(Staff[] staffs) {
        Arrays.sort(staffs, new Comparator<Staff>() {
            @Override
            public int compare(Staff o1, Staff o2) {
                return o1.getDateHired().compareTo(o2.getDateHired());
            }
        });
    }
}