👉 \u60f3\u5b58\u4e00\u5806\u7528\u6237，\u4f46\u53d1\u73b0\u6709\u91cd\u590d\u7684？
\n👉 \u7528 Set \u53bb\u91cd，\u4f46\u7ed3\u679c\u987a\u5e8f\u4e71\u4e86？
\n👉 \u9762\u8bd5\u5b98\u95ee：\u201cHashSet \u548c TreeSet \u6709\u4ec0\u4e48\u533a\u522b？\u201d \u4f60\u53ea\u4f1a\u8bf4\u201c\u4e00\u4e2a\u65e0\u5e8f\u4e00\u4e2a\u6709\u5e8f\u201d？<\/p>\n
\u2705 \u5178\u578b\u573a\u666f：<\/p>\n
+——–+ +——–+ +——–+
\n| Apple | | Banana | | Orange |
\n+——–+ +——–+ +——–+<\/p>\n
\u2705 \u6838\u5fc3\u64cd\u4f5c：<\/p>\n
Set<String> set = new HashSet<>();
\nset.add("Apple");
\nset.add("Banana");
\nset.add("Apple"); \/\/ \u91cd\u590d，\u6dfb\u52a0\u5931\u8d25，\u8fd4\u56de false
\nSystem.out.println(set.size()); \/\/ \u8f93\u51fa 2<\/p>\n
\/\/ HashSet \u5185\u90e8\u6301\u6709\u4e00\u4e2a HashMap
\nprivate transient HashMap<E,Object> map;<\/p>\n
\/\/ add \u65b9\u6cd5\u672c\u8d28\u662f put \u5230 HashMap \u7684 key
\npublic boolean add(E e) {
\n return map.put(e, PRESENT) == null;
\n}<\/p>\n
\u2705 PRESENT \u662f\u4e00\u4e2a\u9759\u6001\u5e38\u91cf，\u6240\u6709 key \u5171\u4eab\u540c\u4e00\u4e2a value\u3002<\/p>\n
HashSet
\n |
\n v
\nHashMap
\n+—————–+
\n| key: "Apple" | -> value: PRESENT (\u5e38\u91cf)
\n+—————–+
\n| key: "Banana" | -> value: PRESENT
\n+—————–+
\n| key: "Orange" | -> value: PRESENT
\n+—————–+<\/p>\n
\u2705 \u53bb\u91cd\u4f9d\u8d56 hashCode() \u548c equals()：<\/p>\n
class User {
\n String name;
\n int age;
\n \/\/ \u672a\u91cd\u5199 hashCode \u548c equals
\n}<\/p>\n
Set<User> users = new HashSet<>();
\nusers.add(new User("Alice", 25));
\nusers.add(new User("Alice", 25)); \/\/ \u88ab\u8ba4\u4e3a\u662f\u4e24\u4e2a\u4e0d\u540c\u7684\u5bf9\u8c61！<\/p>\n
\u2705 \u6b63\u786e\u505a\u6cd5：\u91cd\u5199 hashCode() \u548c equals()，\u786e\u4fdd\u903b\u8f91\u76f8\u7b49\u7684\u5bf9\u8c61\u54c8\u5e0c\u503c\u4e5f\u76f8\u7b49\u3002<\/p>\n
Set<String> set = new LinkedHashSet<>();
\nset.add("C");
\nset.add("A");
\nset.add("B");
\nSystem.out.println(set); \/\/ \u8f93\u51fa [C, A, B]（\u6709\u5e8f！）<\/p>\n
LinkedHashSet
\n |
\n v
\nLinkedHashMap (\u7ee7\u627f HashMap)
\n+—————–+
\n| key: "C" | -> value: PRESENT
\n| (linked to A) |
\n+—————–+
\n| key: "A" | -> value: PRESENT
\n| (linked to B) |
\n+—————–+
\n| key: "B" | -> value: PRESENT
\n| (linked to null)|
\n+—————–+<\/p>\n
\u53cc\u5411\u94fe\u8868：C <-> A <-> B<\/p>\n
\u2705 \u9002\u7528\u573a\u666f：\u9700\u8981\u53bb\u91cd\u4e14\u4fdd\u6301\u63d2\u5165\u987a\u5e8f，\u5982\u6700\u8fd1\u8bbf\u95ee\u8bb0\u5f55\u3001\u914d\u7f6e\u9879\u3002<\/p>\n
Set<Integer> set = new TreeSet<>();
\nset.add(3);
\nset.add(1);
\nset.add(2);
\nSystem.out.println(set); \/\/ \u8f93\u51fa [1, 2, 3]（\u6709\u5e8f！）<\/p>\n
(2)
\n \/ \\\\
\n (1) (3)
\n \/ \\\\ \/ \\\\
\n null null null null<\/p>\n
\u2705 \u6392\u5e8f\u89c4\u5219：<\/p>\n
\/\/ \u81ea\u5b9a\u4e49\u6bd4\u8f83\u5668：\u6309\u5b57\u7b26\u4e32\u957f\u5ea6\u6392\u5e8f
\nSet<String> set = new TreeSet<>((a, b) -> a.length() – b.length());
\nset.add("hi");
\nset.add("hello");
\nset.add("a");
\nSystem.out.println(set); \/\/ \u8f93\u51fa [a, hi, hello]<\/p>\n
\u2705 \u9002\u7528\u573a\u666f：\u9700\u8981\u6392\u5e8f\u7684\u53bb\u91cd\u96c6\u5408，\u5982\u6392\u884c\u699c\u3001\u4f18\u5148\u961f\u5217\u3001\u8303\u56f4\u67e5\u8be2\u3002<\/p>\n
boolean added = set.add("Apple"); \/\/ \u6210\u529f\u8fd4\u56de true，\u91cd\u590d\u8fd4\u56de false<\/p>\n
boolean removed = set.remove("Apple"); \/\/ \u6210\u529f\u8fd4\u56de true，\u4e0d\u5b58\u5728\u8fd4\u56de false<\/p>\n
boolean contains = set.contains("Apple");<\/p>\n
Set<String> set1 = new HashSet<>(Arrays.asList("A", "B", "C"));
\nSet<String> set2 = new HashSet<>(Arrays.asList("B", "C", "D"));<\/p>\n
\/\/ \u5e76\u96c6：set1 \u222a set2
\nSet<String> union = new HashSet<>(set1);
\nunion.addAll(set2); \/\/ [A, B, C, D]<\/p>\n
\/\/ \u4ea4\u96c6：set1 \u2229 set2
\nSet<String> intersection = new HashSet<>(set1);
\nintersection.retainAll(set2); \/\/ [B, C]<\/p>\n
\/\/ \u5dee\u96c6：set1 – set2
\nSet<String> difference = new HashSet<>(set1);
\ndifference.removeAll(set2); \/\/ [A]<\/p>\n
\u7b54：
\nHashSet \u5185\u90e8\u6301\u6709\u4e00\u4e2a HashMap，\u5143\u7d20\u4f5c\u4e3a HashMap \u7684 key \u5b58\u50a8\u3002
\n\u5229\u7528 HashMap \u7684 key \u4e0d\u53ef\u91cd\u590d\u7684\u7279\u6027\u6765\u4fdd\u8bc1 HashSet \u7684\u552f\u4e00\u6027\u3002
\nadd(e) \u672c\u8d28\u662f map.put(e, PRESENT)，PRESENT \u662f\u4e00\u4e2a\u9759\u6001\u5e38\u91cf\u3002<\/p>\n
\u7b54：
\n\u56e0\u4e3a TreeSet \u9700\u8981\u5bf9\u5143\u7d20\u8fdb\u884c\u6bd4\u8f83\u6392\u5e8f\u3002
\n\u5f53\u63d2\u5165 null \u65f6，\u4f1a\u8c03\u7528 compareTo() \u65b9\u6cd5，\u5bfc\u81f4 NullPointerException\u3002
\n\u5373\u4f7f\u7b2c\u4e00\u4e2a\u5143\u7d20\u662f null，\u540e\u7eed\u63d2\u5165\u975e null \u5143\u7d20\u65f6\u4e5f\u4f1a\u5c1d\u8bd5\u4e0e null \u6bd4\u8f83，\u540c\u6837\u4f1a\u629b\u51fa\u5f02\u5e38\u3002<\/p>\n
\u7b54：
\nLinkedHashSet \u7ee7\u627f\u81ea HashSet，\u5e95\u5c42\u4f7f\u7528 LinkedHashMap\u3002
\nLinkedHashMap \u5728 HashMap \u7684\u57fa\u7840\u4e0a，\u589e\u52a0\u4e86\u4e00\u6761\u53cc\u5411\u94fe\u8868，
\n\u5c06\u6240\u6709\u8282\u70b9\u6309\u7167\u63d2\u5165\u987a\u5e8f\u4e32\u8054\u8d77\u6765，\u4ece\u800c\u7ef4\u62a4\u4e86\u63d2\u5165\u987a\u5e8f\u3002<\/p>\n
\u7b54：<\/p>\n
| \u53bb\u91cd，\u6027\u80fd\u4f18\u5148<\/td>\n | HashSet<\/td>\n | \u57fa\u4e8e\u00a0HashMap，O(1)<\/td>\n<\/tr>\n |
| \u53bb\u91cd，\u4fdd\u6301\u63d2\u5165\u987a\u5e8f<\/td>\n | LinkedHashSet<\/td>\n | \u7ef4\u62a4\u53cc\u5411\u94fe\u8868<\/td>\n<\/tr>\n |
| \u53bb\u91cd，\u81ea\u52a8\u6392\u5e8f<\/td>\n | TreeSet<\/td>\n | \u57fa\u4e8e\u7ea2\u9ed1\u6811，O(log n)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \n 🔚 \u6700\u540e\u4e00\u53e5\u8bdd<\/h3>\nSet \u63a5\u53e3\u662f Java \u96c6\u5408\u6846\u67b6\u4e2d\u201c\u53bb\u91cd\u201d\u529f\u80fd\u7684\u57fa\u77f3\u3002 \u5e0c\u671b\u8fd9\u7bc7\u80fd\u5e2e\u4f60\u5f7b\u5e95\u641e\u61c2 Set \u63a5\u53e3\u53ca\u5176\u5e38\u89c1\u5b9e\u73b0！<\/p>\n","protected":false},"excerpt":{"rendered":" \u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb442\u6b21\uff0c\u70b9\u8d5e14\u6b21\uff0c\u6536\u85cf9\u6b21\u3002\u672c\u6587\u5168\u9762\u89e3\u6790Java\u4e2d\u7684Set\u63a5\u53e3\u53ca\u5176\u5b9e\u73b0\u7c7b\uff08HashSet\u3001LinkedHashSet\u3001TreeSet\uff09\u3002Set\u662f\u65e0\u5e8f\u4e14\u4e0d\u5141\u8bb8\u91cd\u590d\u7684\u96c6\u5408\uff0c\u6838\u5fc3\u7279\u6027\u5305\u62ec\uff1a\u57fa\u4e8eequals()\u548chashCode()\u5224\u65ad\u91cd\u590d\uff0c\u4e3b\u8981\u5b9e\u73b0\u7c7b\u6709\u57fa\u4e8e\u54c8\u5e0c\u8868\u7684HashSet\uff08O(1)\u64cd\u4f5c\uff09\u3001\u7ef4\u62a4\u63d2\u5165\u987a\u5e8f\u7684LinkedHashSet\uff08\u53cc\u5411\u94fe\u8868\uff09\u548c\u57fa\u4e8e\u7ea2\u9ed1\u6811\u7684TreeSet\uff08\u81ea\u52a8\u6392\u5e8f\uff0cO(logn)\uff09\u3002\u6587\u7ae0\u8be6\u7ec6\u6bd4\u8f83\u4e86\u4e09\u8005\u7684\u5e95\u5c42\u5b9e\u73b0\u3001\u9002\u7528\u573a\u666f\u548c\u6027\u80fd\u5dee\u5f02\uff0c\u5e76\u63d0\u4f9b\u4e86Set\u7684\u5e38\u7528\u64cd\u4f5c\u65b9\u6cd5\uff08\u6dfb\u52a0\u3001\u5220\u9664\u3001\u4ea4\u96c6\/\u5e76\u96c6\u8fd0\u7b97\uff09\u4ee5\u53ca\u9762\u8bd5\u5e38\u89c1\u95ee\u9898\u89e3\u7b54\u3002<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[99,6003,371,190,176],"topic":[],"class_list":["post-57459","post","type-post","status-publish","format-standard","hentry","category-server","tag-java","tag-javainterview","tag-371","tag-190","tag-176"],"yoast_head":"\n |