java - 非静态变量不能被引用

Question

我试图通过将代码划分为多个函数来使 main() 方法中的代码尽可能精简，因此例如我使用以下函数创建 RentalAgency 类的实例:

/** Creates an Agency with some cars and motorbikes
  */
  public RentalAgency createAgency(){
    List<Vehicle> theVehicles = new ArrayList<Vehicle>();
    Map<Client,Vehicle> rentedVehicles = new HashMap <Client,Vehicle>();
    RentalAgency agency = new RentalAgency(theVehicles, rentedVehicles);
    Vehicle v1 = new Vehicle("Renault","clio",1998,50);
    agency.addVehicle(v1);
    Vehicle v2 = new Vehicle("Renault","twingo",2000,40);
    agency.addVehicle(v2);
    Car c1 = new Car("Renault","scenic",2005, 80, 7);
    agency.addVehicle(c1);
    Car c2 = new Car("Citroen","c3",2006, 70, 5);
    agency.addVehicle(c2);
    MotorBike m1 = new MotorBike("Honda","CB",2015, 50, 500);
    agency.addVehicle(m1);
    MotorBike m2 = new MotorBike("Yamaha","MT",2017, 80, 750);
    agency.addVehicle(m2);
    return agency;
  }

在 main() 中我尝试运行这个:

/**The main function to run the Agency and some renting
  */
    public static void main(String[] args) throws UnknownVehicleException {
      RentalAgency agency = this.createAgency();
    }

但我收到这样的错误:

error: non-static variable this cannot be referenced from a static context RentalAgency agency = this.createAgency();

我真的不知道如何纠正，我查了一下，当您尝试对未启动的东西使用方法时，似乎会发生这种情况？

Answer 1

将方法签名更改为以下内容:

public static RentalAgency createAgency() {...}

您还需要从 main() 方法中删除 this 引用，并只需按以下方式调用该方法:

RentalAgency agency = createAgency();