NavigableSet 无法添加不同的子 class

Question

我有一个 NavigableSet 并想向其中添加两个元素，但是转换失败，如何解决？ AModel 和 BModel 都实现了 BaseModel

 BaseModel AModel = new AModel();

 BaseModel BModel = new BModel();

 NavigableSet<BaseModel > ns = new TreeSet<BaseModel>(Arrays.asList(AModel, BModel));

异常：

  Exception in thread "main" java.lang.ClassCastException: com.simon.main.AModel cannot be cast to java.lang.Comparable
at java.util.TreeMap.compare(Unknown Source)
at java.util.TreeMap.put(Unknown Source)
at java.util.TreeSet.add(Unknown Source)
at java.util.AbstractCollection.addAll(Unknown Source)
at java.util.TreeSet.addAll(Unknown Source)
at java.util.TreeSet.<init>(Unknown Source)
at com.simon.main.Test3.main(Test3.java:18)

基础模型

 public interface BaseModel {

  }

模型

 public class AModel implements BaseModel{

  }

B模型

 public class BModel implements BaseModel{

  }

Answer 1

如果您没有将 Comparator 传递给 TreeSet 构造函数，那么您的元素必须实现 Comparable（并且必须与彼此的类型具有可比性）。 None 个类型是 Comparable。

阅读您正在使用的构造函数的 docs：

All elements inserted into the set must implement the Comparable interface. Furthermore, all such elements must be mutually comparable: e1.compareTo(e2) must not throw a ClassCastException for any elements e1 and e2 in the set.

NavigableSet 无法添加不同的子 class

NavigableSet can't add different sub class

java

collections