我正在学习Java入门课程,我们才刚刚开始学习继承。我正在完成一项任务,要求我们创建一个具有名称和年龄的“宠物”超类。和三个子类,每个子类都有自己的独特特征(我选择了“狗”,“猫”和“鸟”)。构建完所有这些之后,我们将创建一个Main类来测试所有内容,这就是我遇到问题的地方。我试图在中调用get这些独特特征的方法Main,但似乎只能找到超类中的方法。
get
Main
这是主类:
public class Kennel { public static void main(String[] args) { // Create the pet objects Pet cat = new Cat("Feline", 12, "Orange"); Pet dog = new Dog("Spot", 14, "Dalmation"); Pet bird = new Bird("Feathers", 56, 12); // Print out the status of the animals System.out.println("I have a cat named " + cat.getName() + ". He is " + cat.getAge() + " years old." + " He is " + cat.getColor() + "When he speaks he says " + cat.speak()); System.out.println("I also have a dog named " + dog.getName() + ". He is " + dog.getAge() + " years old." + " He is a " + dog.getBreed() + " When he speaks he says " + dog.speak()); System.out.println("And Finally I have a bird named " + bird.getName() + ". He is " + bird.getAge() + " years old." + " He has a wingspan of " + bird.getWingspan() + " inches." + " When he speaks he says " + bird.speak()); } }
这是我的超人
abstract public class Pet { private String name; private int age; // Constructor public Pet(String petName, int petAge) { this.name = petName; this.age = petAge; } // Getters public String getName() { return(this.name); } public int getAge() { return(this.age); } // Setters public void setName(String nameSet) { this.name = nameSet; } public void setAge(int ageSet) { this.age = ageSet; } // Other Methods abstract public String speak(); // toString @Override public String toString() { String answer = "Name: " + this.name + " Age: " + this.age; return answer; } }
这是子类之一(它们看起来都一样并且有相同的错误)
public class Cat extends Pet { private String color; // Constructor public Cat(String petName, int petAge, String petColor) { super(petName, petAge); this.color = petColor; } // Getters public String getColor() { return(this.color); } // Setters public void setColor(String colorSet) { this.color = colorSet; } // Other Methods @Override public String speak() { return "Meow!"; } // toString @Override public String toString() { String answer = "Name: " + super.getName() + " Age: "+super.getAge() + " Color: " + this.color; return answer; } }
因此,发生的事情是我无法找到主要方法来找到该cat.getColor()方法,或者无法找到子类独有的其他方法。
cat.getColor()
当你将变量声明为具有超类的类型时,只能通过该变量访问(公共)方法和超类的成员变量。
Pet cat = new Cat("Feline",12,"Orange"); cat.getName(); // this is OK cat.getColor(); // this is not OK, getColor() is not in Pet
要访问具体类中的方法(Cat在这种情况下),你需要将变量声明为派生类
Cat cat = new Cat("Feline",12,"Orange"); cat.getName(); // OK, getName() is part of Cat (and the superclass) cat.getColor(); // OK, getColor() is part of Cat
或将其转换为你知道/怀疑是具体类型的类型
Pet cat = new Cat("Feline",12,"Orange"); ((Cat)cat).getName(); // OK (same as above) ((Cat)cat).getColor(); // now we are looking at cat through the glass of Cat
你甚至可以结合使用两种方法:
Pet pet = new Cat("Feline",12,"Orange"); Cat cat = (Cat)pet; cat.getName(); // OK cat.getColor(); // OK