理解 Java HashMap 中的树化

Question

我在Java HashMap 源代码中找到了以下代码：

/**
 * The bin count threshold for using a tree rather than list for a
 * bin.  Bins are converted to trees when adding an element to a
 * bin with at least this many nodes. The value must be greater
 * than 2 and should be at least 8 to mesh with assumptions in
 * tree removal about conversion back to plain bins upon
 * shrinkage.
 */
static final int TREEIFY_THRESHOLD = 8;

/**
 * The bin count threshold for untreeifying a (split) bin during a
 * resize operation. Should be less than TREEIFY_THRESHOLD, and at
 * most 6 to mesh with shrinkage detection under removal.
 */
static final int UNTREEIFY_THRESHOLD = 6;

/**
 * The smallest table capacity for which bins may be treeified.
 * (Otherwise the table is resized if too many nodes in a bin.)
 * Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
 * between resizing and treeification thresholds.
 */
static final int MIN_TREEIFY_CAPACITY = 64;

我的疑问是这样的：

Q0。这三个变量如何共同决定树化和非树化？

然而，上述问题可能是抽象的，因为可能涉及许多微妙的事实，需要在答案中解决才能使其整体完整。由于这些是微妙的事实并且可能在答案中被忽略，我试图在下面的三个单独的问题中列出它们。您可以回答 Q0 或最好回答 Q1、Q2 和 Q3。

---

我的理解如下：

我们从冲突解决的链表开始。一旦我们将要散列的键插入到已经包含 8 ( TREEIFY_THRESHOLD) 个键的桶中，并且如果MIN_TREEIFY_CAPACITYHashMap中已经有 64 个 ( ) 键，则该桶的链表将转换为平衡树。如果我们从平衡树中包含 6 个键的桶中删除一个键，那么它会被转换回链表。

一季度。以上理解正确吗？

Q2。我不明白为什么

UNTREEIFY_THRESHOLD 最多应为 6 以在去除下进行收缩检测。

Q3。我不明白为什么

MIN_TREEIFY_CAPACITY应该至少4 * TREEIFY_THRESHOLD避免调整大小和树化阈值之间的冲突。