javaengine

‘壹’ java编程 类的继承及多态

共六个类：Vehicle.java（车类）, Car.java（轿车类）, Bus.java（公共汽车类）, Engine.java（发动机）, VehicleFactory.java（汽车工厂） 和 VehicleTest.java（测试类），具体代码分别如下：

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abstract class Vehicle {
Engine engine;
double speed;
double mileage;

public Vehicle() {
}

public Vehicle(Engine engine) {
this.engine = engine;
}

public Vehicle(Engine engine, double mileage) {
this.engine = engine;
this.mileage = mileage;
}

public Vehicle(Engine engine, double speed, double mileage) {
this.engine = engine;
this.speed = speed;
this.mileage = mileage;
}

public Engine getEngine() {
return engine;
}

public void setEngine(Engine engine) {
this.engine = engine;
}

public double getSpeed() {
return speed;
}

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

public double getMileage() {
return mileage;
}

public void setMileage(double mileage) {
this.mileage = mileage;
}

public double drive() {
this.setMileage(speed * (Math.round(Math.random() * 6)) + mileage);
return mileage;
}

public abstract double calGC();

public String toString() {
return "Type: " + this.getClass().getName() + ", Horsepower: "
+ engine.horsepower + ", Speed: " + speed + ", Mileage: "
+ mileage + ", Gas consumed: " + calGC();
}

}

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public class Car extends Vehicle {
public Car() {

}

public Car(Engine engine) {
this.engine = engine;
}

public Car(Engine engine, double mileage) {
this.engine = engine;
this.mileage = mileage;
}

public Car(Engine engine, double speed, double mileage) {
this.engine = engine;
this.speed = speed;
this.mileage = mileage;
}

public double calGC() {
return mileage * 2;
}
}

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public class Bus extends Vehicle {
public Bus() {

}

public Bus(Engine engine) {
this.engine = engine;
}

public Bus(Engine engine, double mileage) {
this.engine = engine;
this.mileage = mileage;
}

public Bus(Engine engine, double speed, double mileage) {
this.engine = engine;
this.speed = speed;
this.mileage = mileage;
}

public double calGC() {
return mileage * 3 + 20;
}
}

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public class Engine {
double horsepower;

public Engine() {
this.horsepower = 1;
}

public Engine(double horsepower) {
this.horsepower = horsepower;
}

public double getHorsepower() {
return horsepower;
}

public void setHorsepower(double horsepower) {
this.horsepower = horsepower;
}

}

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public class VehicleFactory {
public static Vehicle makeVehicle(Engine e) {
if ((1 <= e.getHorsepower()) && e.getHorsepower() <= 50) {
return new Car(e, 0);
} else if ((50 < e.getHorsepower()) && e.getHorsepower() <= 100) {
return new Bus(e, 0);
}
return null;
}
}

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public class VehicleTest {
public static void main(String[] args) {
// 新建一辆马力28, 速度50的车
Engine e1 = new Engine(28);
Vehicle v1 = VehicleFactory.makeVehicle(e1);
v1.setSpeed(50);
v1.drive();
v1.drive();
System.out.println("第一辆车：");
System.out.println(v1);
// 新建一辆马力88， 速度88的车
Engine e2 = new Engine(88);
Vehicle v2 = VehicleFactory.makeVehicle(e2);
v2.setSpeed(88);
v2.drive();
v2.drive();
System.out.println("第二辆车：");
System.out.println(v2);
}
}

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运行结果如下：

第一辆车：
Type: Car, Horsepower: 28.0, Speed: 50.0, Mileage: 200.0, Gas consumed: 400.0
第二辆车：
Type: Bus, Horsepower: 88.0, Speed: 88.0, Mileage: 616.0, Gas consumed: 1868.0

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