无法访问类型测试的封闭实例。必须在简单的测试程序上使用类型测试错误的封闭实例来限定分配

我得到了类型测试的封闭实例不可访问。必须使用类型测试错误的封闭实例来限定分配Location ob1 = new Location(10.0, 20.0);我不知道为什么..

package pkg;

public class test {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Location ob1 = new Location(10.0, 20.0);
        Location ob2 = new Location(5.0, 30.0);
        ob1.show();
        ob2.show();
        ob1 = ob1.plus(ob2);
        ob1.show();
        return;
    }

    public class Location // an ADT
    {
        private double longitude, latitude;

        public Location(double lg, double lt) {
            longitude = lg;
            latitude = lt;
        }

        public void show() {
            System.out.println(longitude + " " + latitude);
        }

        public Location plus(Location op2) {
            Location temp = new Location(0.0, 0.0);
            temp.longitude = op2.longitude + this.longitude;
            temp.latitude = op2.latitude + this.latitude;
            return temp;
        }
    }
}

try

Location ob1 = new test().new Location(10.0, 20.0);
Location ob2 = new test().new Location(5.0, 30.0);

需要先创建外部类的实例，然后才能创建内部类的实例