Java - Inheritance and Polymorphism

Question

The instructions are these: Create a Main class which will contain the main method. Implement the following inside the main method:

– create objects from the regular classes using the overloaded constructors

– test all instance methods (ie setters, getters, overloaded, overridden)

– a parent reference assigned to a child object

– a method call which passes a polymorphic object

And I got stuck in my Parent Class which is the Rainforest. What should I do next?

Rainforest Class

//INHERITANCE                                                      
  package com.ancient;                                              
  public class Rainforest                                                
  {                                         
  public static void main(String[] args)                                 
  }

Rainforest Class - Inherits Parent and Child

Mammal Class (Parent Class)

//PARENT CLASS                                                     
  package com.ancient;                                              
  public class Mammal                                                    
  {
//INSTANCE VARIABLES
private String type;
private double speed;

//CONSTRUCTOR
public Mammal(String type, double speed)
{
    this.type = type;
    this.speed = speed;
}

//SETTERS
public void setType(String type) 
{
    this.type = type;
}

public void setSpeed(double speed) 
{
    this.speed = speed;
}

//GETTERS
public String getType() 
{
    return type;
}

public double getSpeed() 
{
    return speed;
}

//OVERRIDDEN
public void hunt(int Food)//int Food is the quantity - how many does the eagle he hunts?
{
    System.out.println("The Bald eagle preys " + Food + "animals within a day to survive.");
}

}

Mammal Class - Part 1 Mammal Class - Part 2

Bird (Child Class)

package com.ancient;                                                
 public class Bird extends Mammal                                        
 {                                                                  
 public Bird(String type, double speed) 
{
    super(type, speed);
}

//OVERRIDDING
public void hunt(int Food)//int Food is the quantity - how many does the eagle he hunts?
{
    System.out.println("The Bald eagle will prey " + Food + "animals within a day to survive.");                                                  
}                                                                        
}

Bird - Child Class

My Project content Project content > src > package (library) > regular (2) and main classes (1)

Now, the problem here is: my constructor is undefined. Should I make a new package and insert Rainforest class to it? OR there's something wrong with my object in Mammal and Bird Class?

Answer 1

在Mammal类中有一个接受参数的构造函数，但是您试图在不传递参数的情况下实例化对象。