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mod","2026-09-16T09:13:48.072882Z","PUBLISHED",[118],{"metadata":119,"spec":121,"status":122,"postCount":73},{"name":87,"creationTimestamp":88,"labels":120},{"haloweb.section":90},{"displayName":92,"slug":87,"cover":93,"description":94,"priority":37,"hideFromList":95,"preventParentPostCascadeQuery":95},{"permalink":97,"postCount":73,"visiblePostCount":73},{"metadata":124,"spec":127,"status":134,"categories":138},{"name":125,"creationTimestamp":126},"post-jc-set-impl-56908363","2026-09-13T10:00:55.238233Z",{"title":128,"slug":129,"cover":93,"excerpt":130,"publishTime":131,"categories":132,"tags":133,"priority":27,"pinned":95,"deleted":95,"visible":111,"allowComment":107},"HashSet 和 TreeSet 的区别？","jc-set-impl",{"raw":93,"autoGenerate":107},"2026-09-13T10:00:55.284648Z",[87],[],{"permalink":135,"excerpt":136,"lastModifyTime":137,"phase":116},"\u002Farchives\u002Fjc-set-impl","一、底层实现 HashSet：内部是 HashMap，元素作为 HashMap 的 key，value 是固定 Object。 TreeSet：内部是 TreeMap，基于红黑树。 二、对比 维度 HashSet TreeSet 有序性 无序 自然排序或定制排序 元素要求 重写 equals\u002Fhas","2026-09-16T09:13:47.112793Z",[139],{"metadata":140,"spec":142,"status":143,"postCount":73},{"name":87,"creationTimestamp":88,"labels":141},{"haloweb.section":90},{"displayName":92,"slug":87,"cover":93,"description":94,"priority":37,"hideFromList":95,"preventParentPostCascadeQuery":95},{"permalink":97,"postCount":73,"visiblePostCount":73},{"metadata":145,"spec":148,"status":155,"categories":159},{"name":146,"creationTimestamp":147},"post-jc-hashmap-concurrent-64bd43b8","2026-09-13T10:00:55.033490Z",{"title":149,"slug":150,"cover":93,"excerpt":151,"publishTime":152,"categories":153,"tags":154,"priority":27,"pinned":95,"deleted":95,"visible":111,"allowComment":107},"ConcurrentHashMap 如何保证线程安全？","jc-hashmap-concurrent",{"raw":93,"autoGenerate":107},"2026-09-13T10:00:55.084097Z",[87],[],{"permalink":156,"excerpt":157,"lastModifyTime":158,"phase":116},"\u002Farchives\u002Fjc-hashmap-concurrent","一、JDK 1.7：分段锁 内部是 Segment 数组，每个 Segment 是一个小 HashMap，put 时只锁当前 Segment，并发度 = Segment 数（默认 16）。 二、JDK 1.8：CAS + synchronized 数组节点为空时，用 CAS 插入，无锁。 节点不为空","2026-09-16T09:13:46.058129Z",[160],{"metadata":161,"spec":163,"status":164,"postCount":73},{"name":87,"creationTimestamp":88,"labels":162},{"haloweb.section":90},{"displayName":92,"slug":87,"cover":93,"description":94,"priority":37,"hideFromList":95,"preventParentPostCascadeQuery":95},{"permalink":97,"postCount":73,"visiblePostCount":73},{"metadata":166,"spec":169,"status":176,"categories":180},{"name":167,"creationTimestamp":168},"post-jc-hashmap-principle-21acf5b7","2026-09-13T10:00:54.826428Z",{"title":170,"slug":171,"cover":93,"excerpt":172,"publishTime":173,"categories":174,"tags":175,"priority":27,"pinned":95,"deleted":95,"visible":111,"allowComment":107},"HashMap 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has","2026-09-16T09:13:44.648455Z",[181],{"metadata":182,"spec":184,"status":185,"postCount":73},{"name":87,"creationTimestamp":88,"labels":183},{"haloweb.section":90},{"displayName":92,"slug":87,"cover":93,"description":94,"priority":37,"hideFromList":95,"preventParentPostCascadeQuery":95},{"permalink":97,"postCount":73,"visiblePostCount":73},{"metadata":187,"spec":190,"status":197,"categories":201},{"name":188,"creationTimestamp":189},"post-jc-arraylist-vs-linkedlist-064907ec","2026-09-13T10:00:54.635697Z",{"title":191,"slug":192,"cover":93,"excerpt":193,"publishTime":194,"categories":195,"tags":196,"priority":27,"pinned":95,"deleted":95,"visible":111,"allowComment":107},"ArrayList 和 LinkedList 的区别？","jc-arraylist-vs-linkedlist",{"raw":93,"autoGenerate":107},"2026-09-13T10:00:54.707259Z",[87],[],{"permalink":198,"excerpt":199,"lastModifyTime":200,"phase":116},"\u002Farchives\u002Fjc-arraylist-vs-linkedlist","一、底层结构 ArrayList：基于动态数组，连续内存存储。 LinkedList：基于双向链表，节点分散存储。 二、性能对比 操作 ArrayList LinkedList 随机访问 O(1) O(n) 尾部追加 O(1)（均摊） O(1) 中间插入\u002F删除 O(n)（需移动元素） O(1)（定位","2026-09-16T09:13:43.711113Z",[202],{"metadata":203,"spec":205,"status":206,"postCount":73},{"name":87,"creationTimestamp":88,"labels":204},{"haloweb.section":90},{"displayName":92,"slug":87,"cover":93,"description":94,"priority":37,"hideFromList":95,"preventParentPostCascadeQuery":95},{"permalink":97,"postCount":73,"visiblePostCount":73},{"metadata":208,"spec":209,"status":213,"categories":214,"content":220},{"name":101,"creationTimestamp":102},{"title":104,"slug":105,"cover":93,"excerpt":210,"publishTime":108,"categories":211,"tags":212,"priority":27,"pinned":95,"deleted":95,"visible":111,"allowComment":107},{"raw":93,"autoGenerate":107},[87],[],{"permalink":113,"excerpt":114,"lastModifyTime":115,"phase":116},[215],{"metadata":216,"spec":218,"status":219,"postCount":73},{"name":87,"creationTimestamp":88,"labels":217},{"haloweb.section":90},{"displayName":92,"slug":87,"cover":93,"description":94,"priority":37,"hideFromList":95,"preventParentPostCascadeQuery":95},{"permalink":97,"postCount":73,"visiblePostCount":73},{"content":221,"raw":221},"\u003Ch2>一、定义\u003C\u002Fh2>\n\u003Cp>在用迭代器遍历集合时，如果集合结构被修改（增\u002F删），迭代器会立即抛出 \u003Ccode>ConcurrentModificationException\u003C\u002Fcode>，这就是 fail-fast。\u003C\u002Fp>\n\u003Ch2>二、实现原理\u003C\u002Fh2>\n\u003Cp>集合内部维护 \u003Ccode>modCount\u003C\u002Fcode> 记录结构修改次数。迭代器创建时记录 \u003Ccode>expectedModCount = modCount\u003C\u002Fcode>，每次 \u003Ccode>next()\u003C\u002Fcode> 检查两者是否相等，不等则抛异常。\u003C\u002Fp>\n\u003Ch2>三、触发场景\u003C\u002Fh2>\n\u003Cpre>\u003Ccode class=\"language-java\">List<String> list = new ArrayList<>(Arrays.asList("a","b","c"));\nfor (String s : list) {\n    list.remove(s);   \u002F\u002F 抛 ConcurrentModificationException\n}\n\u003C\u002Fcode>\u003C\u002Fpre>\n\u003Ch2>四、解决方案\u003C\u002Fh2>\n\u003Cul>\n\u003Cli>用 \u003Ccode>Iterator.remove()\u003C\u002Fcode> 删除。\u003C\u002Fli>\n\u003Cli>JUC 的 CopyOnWriteArrayList 是 fail-safe，遍历时修改不抛异常（读的是快照）。\u003C\u002Fli>\n\u003C\u002Ful>"]