vehicle类

public class Vehicle {      double speed;      double size;      Vehicle(){          speed=1.0;          size=2.0;      }      void move(){          }      void setSpeed(int speed){          this.speed=speed;      }      void setSize(int size){          this.size=size;      }      void speedUp(){          speed=speed+1;          System.out.println("汽车加速后的速度为"+speed+"千米/时");      }      void speedDown(){          speed=speed-1;          System.out.println("汽车减速后的速度为"+speed+"千米/时");      }  }  public class test1 {      public static void main(String[] args) {          Vehicle vehicle=new Vehicle();              System.out.println("汽车的速度为"+vehicle.speed+"千米/时");              System.out.println("汽车的体积为"+vehicle.size+"立方米");              vehicle.speedUp();              vehicle.speedDown();      }  }