实例化新的内部类时，内部类不是公共错误

Question

I have this class

package com.rafael;

public class Vehicle {

    public class InnerVehicle {
        InnerVehicle() {
            System.out.println("This is InnerVehicle");
        }
    }
}

And in the main function

import com.rafael.Vehicle;

public class VehicleTest {
    public static void main(String[] args) {
        Vehicle v = new Vehicle();
        Vehicle.InnerVehicle iv = v.new InnerVehicle();
    }
}

But this always gives me that error:

java: InnerVehicle() is not public in com.rafael.Vehicle.InnerVehicle; cannot be accessed from outside package

Answer 1

Make the inner class public static

Otherwise you need an object of your outer class to creat an instance of the inner as Tim Biegeleisen already mentioned

And make the constructor of your inner class public too

Something like:

public class Vehicle {    
    public static class InnerVehicle {
        public InnerVehicle() {
            System.out.println("This is InnerVehicle");
        }
    }
}

Answer 2

You were referring to the nested class incorrectly. You can only instantiate the inner class in the context of the containing class:

Vehicle v = new Vehicle();
InnerVehicle iv = v.new InnerVehicle();

The syntax you were using was for a static nested class, in which case your code would look like this:

public class Vehicle {
    static public class InnerVehicle {
        InnerVehicle() {
            System.out.println("This is InnerVehicle");
        }
    }
}

Vehicle.InnerVehicle iv = new Vehicle.InnerVehicle();