java学习之路 之 高级类特性-抽象类-练习题

/** 具体类 : 对现实世界事物的抽象定义 抽象类 : 对某一类型的不同种事物的抽象定义 */ //编写抽象类Pet, 属性:名字,年龄,体重; 抽象方法speak,eat public abstract class Pet { // 可以包含属性, 构造器,普通方法, 抽象方法 private String name; private int age; private double weight; public Pet() {} public Pet(String name,int age,double weight) { this.name = name; this.age = age; this.weight = weight; } public void setName(String name) { this.name = name; } public String getName() { return name; } public void setAge(int age) { this.age = age; } public int getAge() { return age; } public void setWeight(double weight) { this.weight = weight; } public double getWeight() { return weight; } // 抽象方法 : 只有方法签名没有方法体, 被abstract修饰 public abstract void speak();//抽象方法 public abstract void eat();//抽象方法 @Override public String toString() { return "姓名:" + name + ",年龄:" + age + ",体重:" + weight + "Kg"; } } //编写Bird类继承Pet,特有属性:flySpeed public class Bird extends Pet { private int flySpeed; public Bird() {} public Bird(String name,int age,double weight,int flySpeed) { super(name,age,weight); this.flySpeed = flySpeed; } public void setFlySpeed(int flySpeed) { this.flySpeed = flySpeed; } public int getFlySpeed() { return flySpeed; } // 方法实现!! 去掉abstract 加上方法体 // 具体子类重写并加上方法体抽象父类的抽象方法 @Override public void speak() { System.out.println("叽叽喳喳的叫个不停!!!!"); } @Override public void eat() { System.out.println("最喜欢吃虫子!!!!正在吃虫子中......"); } @Override public String toString() {//父类中toString方法重写 return super.toString() + ",飞行速度:" + flySpeed + "Km/小时!!!"; } } //编写Cat类继承Pet,特有属性:颜色 public class Cat extends Pet { private String color; public Cat() {} public Cat(String name,int age,double weight,String color) { super(name,age,weight); this.color = color; } public void setColor(String color) { this.color = color; } public String getColor() { return color; } @Override public void speak() {// System.out.println("喵喵喵的叫个不停!!!!"); } @Override public void eat() {// System.out.println("最喜欢鱼!!!!正在吃鱼中......"); } @Override public String toString() {//父类中toString方法重写 return super.toString() + ",颜色:" + color; } } //编写Dog类继承Pet,特有属性:品种 public class Dog extends Pet { private String variety; public Dog() {} public Dog(String name,int age,double weight,String variety) { super(name,age,weight); this.variety = variety; } public void setVariety(String variety) { this.variety = variety; } public String getVariety() { return variety; } @Override public void speak() { System.out.println("汪汪汪的叫个不停!!!!"); } @Override public void eat() { System.out.println("最喜欢骨头!!!!正在吃骨头中......"); } @Override public String toString() {//父类中toString方法重写 return super.toString() + ",品种:" + variety; } } /* 创建6个元素的数组，分别存放2个Cat、2个Dog和2个Bird对象 将数组元素按重量倒序排序，然后打印各对象的字符串表示（toString） */ class PetTest { public static void main(String[] args) { //创建6个元素的数组，分别存放2个Cat、2个Dog和2个Bird对象 Pet[] ps = new Pet[6]; //public Cat(String name,int age,double weight,String color) ps[0] = new Cat("小咪",2,2.5,"黑色"); ps[1] = new Cat("二咪",3,3.5,"白色"); //public Dog(String name,int age,double weight,String variety) ps[2] = new Dog("大汪",3,5.5,"泰迪"); ps[3] = new Dog("二汪",2,4.5,"哈巴"); //public Bird(String name,int age,double weight,int flySpeed) ps[4] = new Bird("小叼",2,1.5,30); ps[5] = new Bird("大叼",3,3.0,40); //遍历输出数组 for (Pet p : ps) { System.out.println(p); } System.out.println("-----------------------排序后------------------"); //冒泡法按体重倒序重新排序 for (int i = 0;i < ps.length - 1;i++) { for (int j = 0;j < ps.length - 1 - i;j++）{ if (ps[j].getWeight() < ps[j + 1].getWeight()) { Pet tmp = ps[j]; ps[j] = ps[j + 1]; ps[j + 1] = tmp; } } } //遍历输出数组 for (Pet p : ps) { System.out.println(p); //p.speak(); //p.eat(); } } } public abstract class Frock { private int size; private String color; private double price; public Frock() {} public Frock(int size, String color, double price{ this.size = size; this.color = color; this.price = price; } public void setSize(int size) { this.size = size; } public int getSize() { return size; } public void setColor(String color) { this.color = color; } public String getColor() { return color; } public void setPrice(double price) { this.price = price; } public double getPrice() { return price; } @Override public String toString() { return "尺寸:" + size + ",颜色:" + color + ",价格:" + price; } public abstract double calcArea(); } class Shirt extends Frock { public Shirt() {} public Shirt(int size, String color, double price{ super(size, color, price); } @Override public double calcArea() { return getSize() * 1.3; } } class FrockTest { public static void main(String[] args) { Frock f = new Shirt(180, "白色", 200); System.out.println(f); System.out.println(f.calcArea()); Frock f2 = new Shirt(); System.out.println(f2); System.out.println(f2.calcArea()); } }