Java TreeMap firstEntry()方法的Big O中的运行时复杂性是多少？

import java.util.TreeMap;
import java.util.Map.Entry;

public class TreeMapExample {
    public static void main(String[] args) {
        TreeMap<Integer, String> treeMap = new TreeMap<>();
        treeMap.put(1, "One");
        treeMap.put(3, "Three");
        treeMap.put(2, "Two");

        Entry<Integer, String> firstEntry = treeMap.firstEntry();
        System.out.println("First Entry: " + firstEntry.getKey() + " - " + firstEntry.getValue());
    }
}

First Entry: 1 - One