请定义一个交通工具(Vehicle)的类，其中有:  属性：速度(speed)，体积(size)等  方法：移动(move())，设置速度(setSpeed(int speed))，设置体积（s

package nn;

public class Vehicle {

double speed;
double size;

void move(){
System.out.println("开始移动");
}

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

public void setSize(double size) {
this.size = size;
}

void speedUp(){
speed = speed + 1;
}
void speedDown(){
speed = speed - 1;
}
}

package nn;

public class VehicleTest {

public static void main(String[] args) {
// TODO Auto-generated method stub
Vehicle ss = new Vehicle();
ss.size = 22.1;
ss.speed = 50.6;
ss.move();
System.out.println("体积为："+ss.size+" "+"速度为："+ss.speed);
ss.speedUp();
System.out.println("加速后"+ss.speed);
ss.speedDown();
System.out.println("减速后"+ss.speed);

}

}