深入理解Java多态性：引用类型、实际类型与方法重写

public class Bicycle {
    public int cadence;
    public int gear;
    public int speed;

    public Bicycle(int startCadence, int startSpeed, int startGear) {
        gear = startGear;
        cadence = startCadence;
        speed = startSpeed;
    }

    public void printDescription(){
        System.out.println("\nBike is " + "in gear " + this.gear
                + " with a cadence of " + this.cadence +
                " and travelling at a speed of " + this.speed + ". ");
    }
}

public class MountainBike extends Bicycle {
    private String suspension;

    public MountainBike(
            int startCadence,
            int startSpeed,
            int startGear,
            String suspensionType){
        super(startCadence,
                startSpeed,
                startGear);
        this.setSuspension(suspensionType);
    }

    public void setSuspension(String suspensionType) {
        this.suspension = suspensionType;
    }

    // 方法重写
    @Override
    public void printDescription() {
        super.printDescription();
        System.out.println("The " + "MountainBike has a " +
                getSuspension() + " suspension.");
    }

    public String getSuspension() {
        return suspension;
    }
}

public class Main {
    public static void main(String args[]){
        Object obj = new MountainBike(1,2,3,"soft");
        System.out.println(obj.getClass()); // 输出实际对象类型
        System.out.println(obj.getClass().getSimpleName());
    }
}

public class Main {
    public static void main(String args[]){
        Object obj = new MountainBike(1,2,3,"soft");

        // obj.printDescription(); // 编译错误：Cannot resolve method 'printDescription' in 'Object'
                                 // 因为Object类中没有printDescription方法
    }
}

public class Main {
    public static void main(String args[]){
        Object obj = new MountainBike(1,2,3,"soft");

        ((Bicycle) obj).printDescription(); // 运行时调用的是MountainBike的printDescription
    }
}

// MountainBike类中的重写方法
@Override
public void printDescription() {
    super.printDescription(); // 调用父类Bicycle的printDescription方法
    System.out.println("The " + "MountainBike has a " +
            getSuspension() + " suspension.");
}

class MountainBike
MountainBike

Bike is in gear 3 with a cadence of 1 and travelling at a speed of 2.
The MountainBike has a soft suspension.

// 示例：正确使用@Override注解
public class Child extends Parent {
    @Override
    public void someMethod() {
        // ...
    }
}