对于下面的代码，我尝试根据枚举类型对bean进行排序。此bean的枚举类型也可以为null。
排序后的顺序应为：

A -> B -> C -> null.

运行以下代码后，元素的排序如下：

[A, A, C, B, B, null, C, null]

请帮忙

public class Bean implements Comparable<Bean> {

    enum Type {
      A, B, C
    }

    private Type type;
    private int i;
    private int j;

    public Bean(Type type, int i, int j) {
      this.type = type;
      this.i = i;
      this.j = j;
    }

    @Override
    public int compareTo(Bean that) {
       if (this.type == that.type) {
         return 0;
       }
       if (this.type != null && that.type != null) {
         if (this.type == type.A &&
            that.type == type.B) {
          return -1;
        }
        if (this.type == type.B &&
            that.type == type.C) {
          return -1;
        }
        if (this.type == type.A &&
            that.type == type.C) {
          return -1;
        }
        return 1;
      }

      return this.type == null ? 1 : -1;
    }

    @Override
    public String toString() {
      return "Bean{" + "type=" + (type != null ? type : "Unknown") + "}";
    }

    public static void main(String[] args) {
      Bean b1 = new Bean(Type.B, 1, 1);
      Bean b3 = new Bean(null, 3, 3);
      Bean b2 = new Bean(Type.C, 2, 2);
      Bean b0 = new Bean(Type.A, 0, 0);
      Bean b4 = new Bean(Type.B, 4, 4);
      Bean b5 = new Bean(null, 5, 5);
      Bean b6 = new Bean(Type.C, 6, 6);
      Bean b7 = new Bean(Type.A, 7, 7);

      List<Bean> list = new ArrayList<>();
      list.add(b1);
      list.add(b3);
      list.add(b2);
      list.add(b0);
      list.add(b4);
      list.add(b5);
      list.add(b6);
      list.add(b7);

      System.out.println(list);

      System.out.println(new PriorityQueue<Bean>(list));
    }
}