编码练习——Java-5-接口、继承与多态

基础

定义接口

public interface ICalculate {
final float PI=3.14159f;
float getArea(float r);
float getCircumference(float r);
}

实现接口
- 注意：要实现接口的所有方法（抽象）

public class Cire implements ICalculate {
// 计算圆面积
public float getArea(float r) {
float area = PI*r*r;
return area;
    }
// 计算圆周长
public float getCircumference(float r) {
float circumference = 2*PI*r;
return circumference;
    }
}

实例 - 图片的不同格式保存
定义接口

public interface ImageSaver {
void save();
}

实现接口

public class GIFSaver implements ImageSaver {
//重写 - 多态
@Override
public void save() {
        System.out.println("将图片保存成GIF格式");
    }
}

实例 - 为汽车增加GPS定位功能
父类

public class Car {
private String name;
private double speed;
//省略getXX()和setXX()
public double getSpeed() {
return speed;
    }
@Override
public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("车名：" + name + "，");
        sb.append("速度：" + speed + "千米/小时");
return sb.toString();
    }
}

定义接口

import java.awt.Point;
public interface GPS {
public Point getLocation();
}

实现接口

import java.awt.Point;
public class GPSCar extends Car implements GPS {
@Override
public Point getLocation() {
        Point point = new Point();
        point.setLocation(super.getSpeed(), super.getSpeed());
return point;
    }

@Override 
public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(super.toString());
        sb.append("，坐标：（" + getLocation().x + "," + getLocation().y + "）");
return sb.toString();
    }
}

测试类

import java.awt.Point;
public class Test {
public static void main(String[] args) {
        GPSCar gcar = new GPSCar();
        Point point = gcar.getLocation();
        System.out.println("坐标：（" + point.x + "," + point.y + "）");
        String info = gcar.toString();
        System.out.println(info);
    }
}

继承

public class Test {
public static void main(String[] args) {
        Pigeon pigeon = new Pigeon();
        System.out.println(pigeon.color);
    }
}

// 父类
class Bird {
    String color = "白色";
    String skin = "羽毛";
}
// 子类 - 继承（属性和方法）
class Pigeon extends Bird {
}

继承-重写

public class Test {
public static void main(String[] args) {
        Dog dog = new Dog();
        System.out.println("执行dog.cry();语句时的输出结果：");
        dog.cry();
        Cat cat = new Cat();
        System.out.println("执行cat.cry();语句时的输出结果：");
        cat.cry();
        Sheep sheep = new Sheep();
        System.out.println("执行cat.cry();语句时的输出结果：");
        sheep.cry();
    }
}

// 父类
class Animal {
public Animal() {

    }

public void cry() {
        System.out.println("动物发出叫声！");
    }
}
// 子类
class Dog extends Animal {
public Dog() {

    }

public void cry() {
        System.out.println("狗发出“汪汪...”声！");
    }
}
// 子类
class Cat extends Animal {
public Cat(){

    }

public void cry() {
        System.out.println("猫发出“喵喵...”声！");
    }
}
// 子类
class Sheep extends Animal {

}

调用父类的构造函数、成员变量和成员方法

public class Test {
public static void main(String[] args) {
        Tiger tiger = new Tiger();
        System.out.println("Tiger的皮肤：" + tiger.skin);
        tiger.test();
    }
}

// 父类
class Beast {
    String skin = "";
public Beast() {    //无参构造函数

    }
public Beast(String strSkin) {
        skin = strSkin;
    }
public void move() {
        System.out.println("跑");
    }
}
// 子类 - 继承（属性和方法）
class Tiger extends Beast {
public Tiger() {
super("条纹");    //使用父类带参数的构造方法
    }
public void test() {
        System.out.println("父类的肤色：" + super.skin);
        System.out.println("父类的动作跑：");
super.move();
    }
}

实例 - 经理（子类）和员工（父类）的差异

import java.util.Date;
public class Test {
public static void main(String[] args) {
        Employee employee = new Employee();
        employee.setName("Java");
        employee.setSalary(100);
        employee.setBirthday(new Date());
        Manager manager = new Manager();
        manager.setName("明日科技");
        manager.setSalary(3000);
        manager.setBirthday(new Date());
        manager.setBonus(2000);
//输出经理和员工的属性值
        System.out.println("员工的姓名：" + employee.getName());
        System.out.println("员工的工资：" + employee.getSalary());
        System.out.println("员工的生日：" + employee.getBirthday());
        System.out.println("经理的姓名：" + manager.getName());
        System.out.println("经理的工资：" + manager.getSalary());
        System.out.println("经理的生日：" + manager.getBirthday());
        System.out.println("经理的奖金：" + manager.getBonus());
    }
}

// 父类
class Employee {
private String name;
private double salary;
private Date birthday;
public String getName() {
return name;
    }
public void setName(String name) {
this.name = name;
    }
public double getSalary() {
return salary;
    }
public void setSalary(double salary) {
this.salary = salary;
    }
public Date getBirthday() {
return birthday;
    }
public void setBirthday(Date birthday) {
this.birthday = birthday;
    }
}
// 子类 - 继承（属性和方法）
class Manager extends Employee {
private double bonus;
public double getBonus() {
return bonus;
    }
public void setBonus(double bonus) {
this.bonus = bonus;
    }
}

实例 - 重写父类中的方法

public class Test {
public static void main(String[] args) {
        Employee employee = new Employee();
        System.out.println(employee.getInfo());
        Manager manager = new Manager();
        System.out.println(manager.getInfo());
    }
}

// 父类
class Employee {
public String getInfo() {
return "父类：我是明日科技的员工！";
    }
}
// 子类 - 重写
class Manager extends Employee {
@Override
public String getInfo() {
return "子类：我是明日科技的经理！";
    }
}

多态

public class Test {
final float PI=3.14159f;
// 求圆形的面积
public float getArea(float r) {
float area = PI*r*r;
return area;
    }
// 求矩形的面积
public float getArea(float l, float w) {
float area = l*w;
return area;
    }
// 画任意形状的图形
public void draw(int num) {
        System.out.println("画" + num + "个任意形状的图形");
    }
// 画指定形状的图形
public void draw(String shape) {
        System.out.println("画一个" + shape);
    }

public static void main(String[] args) {
        Test test = new Test();
float l=20;
float w=30;
float areaRectangle = test.getArea(l, w);
        System.out.println("求长为"+l+" 宽为"+w+"的矩形的面积是：" + areaRectangle);
float r = 7;
float areaCirc = test.getArea(r);
        System.out.println("求半径为"+r+"的圆的面积是："+areaCirc);
int num=7;
        test.draw(num);
        test.draw("三角形");
    }
}

实例 - 计算几何图形的面积

public class Test {
public static void main(String[] args) {
        Circle circle = new Circle(1);
        System.out.println("图形的名称是：" + circle.getName());
        System.out.println("图形的面积是：" + circle.getArea());

        Rectangle rectangle = new Rectangle(1, 1);
        System.out.println("图形的名称是：" + rectangle.getName());
        System.out.println("图形的面积是：" + rectangle.getArea());
    }
}

// 父类
abstract class Shape {
public String getName() {
return this.getClass().getSimpleName(); //获得图形的名称
    }
public abstract double getArea();   //获得图形的面积
}
// 子类
class Circle extends Shape {
private double radius;
public Circle(double radius) {
this.radius = radius;
    }
@Override
public double getArea(){
return Math.PI*Math.pow(radius, 2);
    }
}
// 子类
class Rectangle extends Shape {
private double length;
private double width;
public Rectangle(double length, double width) {
this.length = length;
this.width = width;
    }
@Override
public double getArea() {
return length * width;
    }
}

实例 - 简单的汽车销售商场

public class Test {
public static void main(String[] args) {
        System.out.println("顾客要购买BMW：");
        Car bmw = CarFactory.getCar("BMW");
        System.out.println("提取汽车：" + bmw.getInfo());

        System.out.println("顾客要购买Benz：");
        Car benz = CarFactory.getCar("Benz");
        System.out.println("提取汽车：" + benz.getInfo());
    }
}

// 父类
abstract class Car {
public abstract String getInfo();
}
// 子类
class BMW extends Car {
@Override
public String getInfo() {
return "BMW";
    }
}
// 子类
class Benz extends Car {
@Override
public String getInfo() {
return "Benz";
    }
}
// 工厂
class CarFactory {
public static Car getCar(String name) {
if (name.equalsIgnoreCase("BMW")) {
return new BMW();
        } else if (name.equalsIgnoreCase("Benz")) {
return new Benz();
        } else {
return null;
        }
    }
}

实例 - 使用Comparable接口自定义排序

public class Employee implements Comparable<Employee> {
private int id;
private String name;
private int age;
public Employee(int id, String name, int age) { // 构造函数
this.id = id;
this.name = name;
this.age = age;
    }
@Override
public int compareTo(Employee o) {
if (id > o.id) {
return 1;
        } else if (id < o.id) {
return -1;
        }
return 0;
    }
@Override
public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("员工的编号：" + id + "，");
        sb.append("员工的姓名：" + name + "，");
        sb.append("员工的年龄：" + age);
return sb.toString();
    }

public static void main(String[] args) {
        Employee employee1 = new Employee(1000,"学志", 27);
        Employee employee2 = new Employee(1001,"珊妮", 27);
        System.out.println("比较结果：" + employee1.compareTo(employee2));
        System.out.println("员工信息：" + employee1.toString());
    }
}from: http://blog.csdn.net/xuezhisdc/article/details/52188292

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编码练习——Java-5-接口、继承与多态

基础

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