可比和通用

Question

When this class is created..

public static class TreeNode<E extends Comparable<E>>

what does the <E extends Comparable<E>> mean?

Answer 1

That is a generic constraint.

It means that whatever type you store in the TreeNode must implement the Comparable<E> interface.

Answer 2

It means that whenever you create an instance of this class like

TreeNode<MyClass> myTreeNode = new TreeNode<MyClass>();

MyClass must implement Comparable < MyClass >

public class MyClass implements Comparable<MyClass>
{
      //CODE
}