作为一个Java初学者，如何定义一个父类Employee，然后创建两个子类Manager和Employee（Manager继承自Employee），并展示相关的类结构和实例化代码？

首先，让我们定义一个简单的`Employee`父类，它可能会包含一些通用的属性和方法，如姓名、职位等：

public abstract class Employee {
    private String name;
    private String position;

    public Employee(String name, String position) {
        this.name = name;
        this.position = position;
    }

    // getters and setters for name and position
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public String getPosition() { return position; }
    public void setPosition(String position) { this.position = position; }

    // 定义一个抽象方法用于展示员工基本信息
    public abstract void displayInfo();
}

接着，我们创建`Manager`子类，它继承自`Employee`并覆盖了父类的`displayInfo`方法：

public class Manager extends Employee {
    private int employeeId;

    public Manager(String name, String position, int employeeId) {
        super(name, position);
        this.employeeId = employeeId;
    }

    @Override
    public void displayInfo() {
        System.out.println("Manager: " + getName() + ", ID: " + employeeId);
    }
}

最后，我们创建一个普通的`Employee`子类，同样继承自`Employee`：

public class Employee extends Employee {
    private String department;

    public Employee(String name, String position, String department) {
        super(name, position);
        this.department = department;
    }

    @Override
    public void displayInfo() {
        System.out.println(getName() + ", Position: " + getPosition());
    }
}

现在我们可以实例化这两个子类：

public static void main(String[] args) {
    Manager manager = new Manager("John Doe", "Manager", 12345);
    manager.displayInfo(); // 输出: Manager: John Doe, ID: 12345

    Employee regularEmployee = new Employee("Jane Smith", "Developer", "IT");
    regularEmployee.displayInfo(); // 输出: Jane Smith, Position: Developer
}