ADDITIONAL SYSTEM INFORMATION :
openjdk version "24-ea" 2025-03-18
OpenJDK Runtime Environment (build 24-ea+21-2447)
OpenJDK 64-Bit Server VM (build 24-ea+21-2447, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
Proposing a minor improvement that I could suggest based on my learnings from making use of the public API `ceilingEntry`.
    /**
     * Gets the entry corresponding to the specified key; if no such entry
     * exists, returns the entry for the least key greater than the specified
     * key; if no such entry exists (i.e., the greatest key in the Tree is less
     * than the specified key), returns {@code null}.
     */
```
It is not clear from the documentation that the value returned is upon the existence of the key.