抽象类
abstract 修饰符 返回值类 方法名(参数列表)
1.抽象类中可以没有抽象方法，有抽象方法的类一定是抽象类
2.抽象类本身不能创建对象，只能依靠子类向上转型方式创建
抽象类的子类：继承了抽象类的类，抽象类的子类要么实现抽象类中所有的抽象方法，要么自己本身是一个抽象类，实现抽象方法：在子类中重写父类中的抽象方法，给出具体方法体。
3.抽象类不能使用final修饰。抽象方法也不能使用static修饰
4.抽象类中有构造方法的。完成数据初始化，为了让子类调用
package chouxiang;
public class AbstractDemo1 {
public static void main(String[] args) {
Animal a = new Cat(); // 向上转型，也叫抽象类的多态
a.sleep();
}
}
abstract class Animal{
abstract public void sleep();
}
class Cat extends Animal{
// 重写sleep方法
public void sleep() {
System.out.println("睡觉了啊！");
}
}
package chouxiang;
public class AbstractDemo2 {
public static void main(String[] args) {
// 使用抽象类的多态，调用方法
A a = new B();
a.a();
a.b();
}
}
abstract class A{
// 定义2个抽象类
abstract public void a();
abstract public void b();
}
class B extends A{
// 子类实现2个抽象类方法
public void a() {
System.out.println("打印A");
}
public void b() {
System.out.println("打印B");
}
}
package chouxiang;
public class AbstractDemo3 {
public static void main(String[] args) {
Shape r = new Rect(20, 10);
Shape c = new Circle(5);
print(r);
print(c);
}
public static void print(Shape s) {
System.out.println("周长为:" + s.Primeter());
System.out.println("面积为:" + s.area());
}
}
abstract class Shape{
abstract public double Primeter();
abstract public double area();
}
class Rect extends Shape{
double length;
double width;
public Rect() {
}
public Rect(double length, double width) {
this.length = length;
this. width = width;
}
@Override
public double Primeter() {
return 2*(length + width);
}
@Override
public double area() {
return length*width;
}
}
class Circle extends Shape{
double r;
public static final double PI = 3.14;
public Circle() {
}
public Circle(double r) {
this.r = r;
}
@Override
public double Primeter() {
return 2 * PI * r;
}
@Override
public double area() {
return PI * r * r;
}
}
package chouxiang;
public class AbstractDemo4 {
public static void main(String[] args) {
Person p = new Person();
p.setName("小明");
p.setAge(18);
p.setGender('男');
Phone m = new Phone();
m.setBrand("小米");
m.setColor("绿色");
m.setPrice(1999);
m.setType("米8");
p.setPhone(m);
Person p2 = new Person("小王",22,'女',new Phone("苹果", "11","绿色", 4999));
p.show();
p2.show();
}
}
class Phone{
private String brand;
private String type;
private String color;
private double price;
// 无参构造方法
public Phone() {
super();
}
// 有参构造方法
public Phone(String brand, String type, String color, double price) {
super();
this.brand = brand;
this.type = type;
this.color = color;
this.price = price;
}
public String getBrand() {
return brand;
}
public void setBrand(String brand) {
this.brand = brand;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
}
// Person 和 Phone关系为组合关系
class Person{
private String name;
private int age;
private char gender;
private Phone phone;
public Person() {
super();
}
public Person(String name, int age, char gender, Phone phone) {
super();
this.name = name;
this.age = age;
this.gender = gender;
this.phone = phone;
}
public void show() {
System.out.println("姓名:" + name + "，年龄:" + age + ", 性别:" + gender + ",手机信息:" + phone.getBrand()+ "_" + phone.getColor()+ "_" + phone.getPrice() + "_"+ phone.getType());
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public char getGender() {
return gender;
}
public void setGender(char gender) {
this.gender = gender;
}
public Phone getPhone() {
return phone;
}
public void setPhone(Phone phone) {
this.phone = phone;
}
}
