Java 标识符不工作

Question

所以我有一个汽车类(class)和一个汽车测试员类(class)。这是汽车类别:

package main;

public class Car {

    private long distance;
    private double newDistance;
    private double gasAmount;
    private double newGasAmount;

    // Contrsuctor 
    Car(){
        distance = 0;
    }


    Car(long newDistance){
        distance = newDistance;
    }
    //Accessor
    public long getDistance(){
        return distance;
    }

    public double getGasInTank(){
        return gasAmount;
    }

    //Mutator
    public void drive(double distance){
        newDistance = distance;
    }    
    public void addGas(double gasAmount){
        newGasAmount = gasAmount;
    }
}

问题就在这里。在我的 carTester 类中，为什么 myVehicle.drive(); 不起作用？它用红色下划线 (netBeans) 并显示“包 myVehicle 不存在”

package main;

public class CarTester {

    Car myVehicle = new Car();
    myVehicle.drive();
    double gasLeft = myVehicle.getGasInTank();
}

Answer 1

当您尝试在类 block 中的对象上调用操作时，编译器将发出此消息。

您需要使用CarTester中的main方法。此外，您还需要根据您的 drive 方法提供一个 double distance 值。

public class CarTester {
  public final static void main(String[] args) {
    Car myVehicle = new Car();
    myVehicle.drive(33.2);
    ...
  }
}