Java抽象类、继承和封装：Role、Employee和Manager类的示例

"抽象类是一种不能被实例化的类，它用于定义一个共性的概念，具体的实现由子类来完成。抽象类可以包含抽象方法和具体方法，抽象方法只有声明而没有实现，需要由子类来实现。\n\n继承是面向对象的重要特性，它允许一个类继承另一个类的属性和方法，从而实现代码的复用。子类可以继承父类的成员变量和方法，并可以通过重写方法来改变父类的行为。\n\n封装是将数据和操作数据的方法封装在一起，对外部只暴露必要的接口，隐藏内部的实现细节。通过封装，可以提高代码的可维护性和安全性。\n\n构造器是类的特殊方法，用于创建对象时初始化对象的成员变量。构造器的名称与类名相同，没有返回值类型。\n\n接口是一种抽象类型，它定义了一组方法的签名，但没有具体的实现。一个类可以实现多个接口，从而具备多个接口定义的方法。接口可以用于实现多态。\n\n下面是根据题目要求定义的代码：\n\njava\n// 抽象类 Role\npublic abstract class Role {\n private String name;\n private int age;\n private String gender;\n\n public Role() {\n System.out.println(\"调用了无参构造方法\");\n }\n\n public Role(String name, int age, String gender) {\n this.name = name;\n this.age = age;\n this.gender = gender;\n System.out.println(\"调用了有参构造方法\");\n }\n\n public String getName() {\n return name;\n }\n\n public void setName(String name) {\n this.name = name;\n }\n\n public int getAge() {\n return age;\n }\n\n public void setAge(int age) {\n this.age = age;\n }\n\n public String getGender() {\n return gender;\n }\n\n public void setGender(String gender) {\n this.gender = gender;\n }\n\n public abstract void play();\n}\n\n\n// Employee 类继承 Role 类\npublic class Employee extends Role {\n private int salary;\n private static int ID;\n\n public Employee() {\n super();\n System.out.println(\"调用了 Employee 的无参构造方法\");\n }\n\n public Employee(String name, int age, String gender, int salary) {\n super(name, age, gender);\n this.salary = salary;\n System.out.println(\"调用了 Employee 的有参构造方法\");\n }\n\n public int getSalary() {\n return salary;\n }\n\n public void setSalary(int salary) {\n this.salary = salary;\n }\n\n public static int getID() {\n return ID;\n }\n\n public static void setID(int ID) {\n Employee.ID = ID;\n }\n\n @Override\n public void play() {\n System.out.println(\"Employee playing\");\n }\n\n public final void sing() {\n System.out.println(\"Employee singing\");\n }\n}\n\n\n// Manager 类继承 Employee 类\npublic class Manager extends Employee {\n private final String vehicle;\n\n public Manager() {\n super();\n this.vehicle = \"Car\";\n System.out.println(\"调用了 Manager 的无参构造方法\");\n }\n\n public Manager(String name, int age, String gender, int salary, String vehicle) {\n super(name, age, gender, salary);\n this.vehicle = vehicle;\n System.out.println(\"调用了 Manager 的有参构造方法\");\n }\n\n public String getVehicle() {\n return vehicle;\n }\n\n @Override\n public void play() {\n System.out.println(\"Manager playing\");\n }\n}\n\n\npublic class Main {\n public static void main(String[] args) {\n Role role = new Employee();\n role.play(); // Employee playing\n\n Employee employee = new Employee(\"John\", 30, \"Male\", 5000);\n employee.play(); // Employee playing\n employee.sing(); // Employee singing\n\n Manager manager = new Manager(\"Alice\", 35, \"Female\", 10000, \"Car\");\n manager.play(); // Manager playing\n manager.sing(); // Employee singing\n }\n}\n\n\n在main()方法中，我们创建了一个Role对象，由于Role是抽象类，不能直接实例化，所以我们实例化了一个Employee对象，然后调用了play()方法。接下来，我们创建了一个Employee对象，调用了play()方法和sing()方法。最后，我们创建了一个Manager对象，调用了play()方法和sing()方法。注意，由于sing()方法在Employee中被声明为final，所以在Manager中不能被重写。