超类与子类

以员工类为超类如下：

//员工类（超类）
import java.time.LocalDate;
public class Employee {
    //定义超类员工类（Employee）的字段
    private final String name; // 姓名
    private double salary; // 薪水
    private final LocalDate hireDay; // 入职日期

    //初始化员工各个字段
    public Employee(String name, double salary, int year, int month, int day) {
            this.name = name;
            this.salary = salary;
            hireDay = LocalDate.of(year, month, day);
    }

    //各个字段返回值
    public String getName() {
            return name;
    }

    public double getSalary() {
            return salary;
    }

    public LocalDate getHireDay() {
            return hireDay;
    }

    //计算提薪
    public void raiseSalary(double byPercent) {
            double raise = salary * byPercent / 100;
            salary += raise;
    }
}

以这个员工类为基础，写经理类，，经理工资在员工基本工资的基础上，额外加上奖金，如下：

// 经理类（子类）继承员工类（超类）
public class Manager extends Employee{
    private double bonus; // 奖金

    public Manager(String name, double salary, int year, int month, int day) {
        super(name, salary, year, month, day);
    }
    //经理工资
    public double getSalary() {
        double baseSalary = super.getSalary(); // 获取基本工资
        return baseSalary + bonus; // 薪水=基本工资+奖金
    }
    //奖金初始化
    public void setBonus(double bonus) {
        this.bonus = bonus;
    }
}

最后我们进行测试，用员工和经理做比对：

//进行测试
public class ManagerTest {
    public static void main(String[] args) {
        //构造对象
        Manager boss = new Manager("张三", 18000, 2000, 12, 15);
        boss.setBonus(500);

        Employee e = new Employee("李四", 5500, 2020, 10, 1);
        System.out.printf("%s, %.2f\n", e.getName(), e.getSalary());
        // => 李四, 5500.00

        e = boss;
        System.out.printf("%s, %.2f\n", e.getName(), e.getSalary());
        // => 张三, 18500.00
    }
}

总结：利用JAVA中的 ” 继承 “ 机制，让子类继承超类的内容，大大减少了重复代码，使代码更加简洁明了。