我不能从内部单例访问外部类var吗？

public class OuterClass {
    private String outerVar = "Hello from OuterClass";

    public class InnerSingleton {
        private static InnerSingleton instance;

        private InnerSingleton() {
            // 可以访问外部类的变量
            System.out.println(outerVar);
        }

        public static InnerSingleton getInstance() {
            if (instance == null) {
                instance = new InnerSingleton();
            }
            return instance;
        }
    }

    public static void main(String[] args) {
        // 创建外部类实例
        OuterClass outer = new OuterClass();
        // 获取内部单例实例
        InnerSingleton innerSingleton = outer.InnerSingleton.getInstance();
    }
}