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Update Java 容器.md

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补充 HashMap 扩容时桶下标变化的示意图。
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CyC2018
2026-10-25 19:34:23 +08:00
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commit 5422b53ef0
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notes/Java 容器.md
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@@ -754,6 +754,8 @@ new capacity : 00100000
- 为 0，那么 hash%00010000 = hash%00100000，桶位置和原来一致；
- 为 1，hash%00100000 = hash%00010000 + 16，桶位置是原位置 + 16。
<div align="center"> <img src="pics/hashmap-resize.png" width="560px"/> </div><br>
#### 7. 计算数组容量
HashMap 构造函数允许用户传入的容量不是 2 的 n 次方，因为它可以自动地将传入的容量转换为 2 的 n 次方。
notes/pics/hashmap-resize.png
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tools/diagram/src/hashmap-resize.svg
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<svg xmlns="http://www.w3.org/2000/svg" width="620" height="290" viewBox="0 0 620 290">
<style>
text { font-family: "PingFang SC", "Microsoft YaHei", Helvetica, Arial, sans-serif; fill: #666; font-size: 12px; }
.title { font-weight: bold; font-size: 15px; fill: #777; text-anchor: middle; }
.b { font-weight: bold; }
.c { text-anchor: middle; }
.e { text-anchor: end; }
.note { fill: #C0605A; }
.ok { fill: #6A9F68; }
.sub { font-size: 11px; fill: #888; }
.mono { font-family: Menlo, Consolas, monospace; }
.arrow { stroke: #666; stroke-width: 1.3; fill: none; marker-end: url(#a); }
.red { stroke: #C0605A; marker-end: url(#r); }
.green { stroke: #6A9F68; marker-end: url(#g); }
.dash { stroke-dasharray: 5 4; }
.line { stroke: #666; stroke-width: 1.3; fill: none; }
.frame { fill: none; stroke: #999; stroke-width: 1; stroke-dasharray: 4 3; }
.shadow { fill: #C0C0C0; }
</style>
<defs>
<marker id="a" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
<path d="M1,1 L9,5 L1,9" fill="none" stroke="#666" stroke-width="1.6"/>
</marker>
<marker id="r" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
<path d="M1,1 L9,5 L1,9" fill="none" stroke="#C0605A" stroke-width="1.6"/>
</marker>
<marker id="g" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
<path d="M1,1 L9,5 L1,9" fill="none" stroke="#6A9F68" stroke-width="1.6"/>
</marker>
</defs>
<rect width="100%" height="100%" fill="#FFFFFF"/>
<text x="310" y="28" class="title">HashMap 扩容时的桶下标</text>
<rect x="150" y="70" width="20" height="24" fill="#FFFFFF" stroke="#999"/>
<rect x="170" y="70" width="20" height="24" fill="#FFFFFF" stroke="#999"/>
<rect x="190" y="70" width="20" height="24" fill="#FFFFFF" stroke="#999"/>
<rect x="210" y="70" width="20" height="24" fill="#FFFFFF" stroke="#999"/>
<rect x="230" y="70" width="20" height="24" fill="#FFFFFF" stroke="#999"/>
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<text x="140" y="87" class="e">capacity = 16</text>
<text x="160" y="64" class="c sub">0</text>
<text x="260" y="64" class="c sub">5</text>
<text x="460" y="64" class="c sub">15</text>
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<text x="130" y="237" class="e">capacity = 32</text>
<text x="147" y="260" class="c sub">0</text>
<text x="217" y="260" class="c sub">5</text>
<text x="441" y="260" class="c sub">21</text>
<text x="581" y="260" class="c sub">31</text>
<line x1="257" y1="97" x2="217" y2="217" class="arrow "/>
<line x1="263" y1="97" x2="441" y2="217" class="arrow "/>
<text x="205" y="150" class="e mono">hash 低 5 位 0 0101</text>
<text x="205" y="168" class="e ok">第 5 位为 0：仍在 5</text>
<text x="371" y="150" class="mono">hash 低 5 位 1 0101</text>
<text x="371" y="168" class="note">第 5 位为 1：移到 5 + 16 = 21</text>
<text x="310" y="280" class="c">桶 5 中的键值对扩容后只会落在 5 或 21</text>
</svg>
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