How HashMap works internally in java<\/figcaption><\/figure>\nL\u1edbp HashMap h\u1ed7 tr\u1ee3 4 ph\u01b0\u01a1ng th\u1ee9c t\u1ea1o\/kh\u1edfi t\u1ea1o \u0111\u1ed1i t\u01b0\u1ee3ng. Ph\u01b0\u01a1ng th\u1ee9c \u0111\u1ea7u ti\u00ean \u0111\u1ec3 t\u1ea1o\/kh\u1edfi t\u1ea1o m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng HashMap l\u00e0 x\u00e2y d\u1ef1ng m\u1ed9t b\u1ea3ng b\u0103m ng\u1ea7m \u0111\u1ecbnh:<\/p>\n
HashMap()<\/pre>\nPh\u01b0\u01a1ng th\u1ee9c th\u1ee9 hai kh\u1edfi t\u1ea1o m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng HashMap b\u1eb1ng vi\u1ec7c s\u1eed d\u1ee5ng m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng HashMap kh\u00e1c, c\u00f2n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 h\u00e0m t\u1ea1o sao ch\u00e9p.<\/p>\n
HashMap(Map m)\r\n<\/pre>\nPh\u01b0\u01a1ng th\u1ee9c th\u1ee9 ba kh\u1edfi t\u1ea1o m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng b\u1ea3ng b\u0103m v\u1edbi s\u1ee9c ch\u1ee9a (capacity) c\u1ee5 th\u1ec3.<\/p>\n
HashMap(int capacity)<\/pre>\nPh\u01b0\u01a1ng th\u1ee9c th\u1ee9 t\u01b0 kh\u1edfi t\u1ea1o m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng b\u1ea3ng b\u0103m v\u1edbi hai tham s\u1ed1 s\u1ee9c ch\u1ee9a (capacity) v\u00e0 t\u1ec9 l\u1ec7 l\u00e0m \u0111\u1ea7y b\u1ea3ng b\u0103m (fillRatio).<\/p>\n
HashMap(int capacity, float fillRatio)<\/pre>\nM\u1ed9t s\u1ed1 ph\u01b0\u01a1ng th\u1ee9c \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a th\u00eam trong l\u1edbp HashMap<\/p>\n
Ngo\u00e0i nh\u1eefng ph\u01b0\u01a1ng th\u1ee9c k\u1ebf th\u1eeba t\u1eeb c\u00e1c l\u1edbp cha, l\u1edbp HashMap \u0111\u1ecbnh ngh\u0129a th\u00eam nh\u1eefng ph\u01b0\u01a1ng th\u1ee9c sau:<\/p>\n
VD: V\u00ed d\u1ee5 sau \u0111\u00e2y minh h\u1ecda m\u1ed9t v\u00e0i ph\u01b0\u01a1ng th\u1ee9c m\u00e0 l\u1edbp n\u00e0y h\u1ed7 tr\u1ee3.<\/p>\n
import java.util.*;\r\n\r\npublic class HashMapDemo {\r\n\r\n public static void main(String args[]) {\r\n \r\n \/\/ Create a hash map\r\n HashMap hm = new HashMap();\r\n \/\/ Put elements to the map\r\n hm.put(\"Zara\", new Double(3434.34));\r\n hm.put(\"Mahnaz\", new Double(123.22));\r\n hm.put(\"Ayan\", new Double(1378.00));\r\n hm.put(\"Daisy\", new Double(99.22));\r\n hm.put(\"Qadir\", new Double(-19.08));\r\n \r\n \/\/ Get a set of the entries\r\n Set set = hm.entrySet();\r\n \/\/ Get an iterator\r\n Iterator i = set.iterator();\r\n \/\/ Display elements\r\n while(i.hasNext()) {\r\n Map.Entry me = (Map.Entry)i.next();\r\n System.out.print(me.getKey() + \": \");\r\n System.out.println(me.getValue());\r\n }\r\n System.out.println();\r\n \/\/ Deposit 1000 into Zara's account\r\n double balance = ((Double)hm.get(\"Zara\")).doubleValue();\r\n hm.put(\"Zara\", new Double(balance + 1000));\r\n System.out.println(\"Zara's new balance: \" +\r\n hm.get(\"Zara\"));\r\n }\r\n}<\/pre>\nCh\u01b0\u01a1ng tr\u00ecnh n\u00e0y s\u1ebd sinh ra k\u1ebft qu\u1ea3 nh\u01b0 sau:<\/p>\n
Zara: 3434.34\r\nMahnaz: 123.22\r\nDaisy: 99.22\r\nAyan: 1378.0\r\nQadir: -19.08\r\n\r\nZara's new balance: 4434.34<\/pre>\n<\/span>Tham kh\u1ea3o th\u00eam:<\/span><\/h2>\nhttps:\/\/docs.oracle.com\/javase\/8\/docs\/api\/java\/util\/HashMap.html<\/p>\n
http:\/\/examples.javacodegeeks.com\/core-java\/util\/hashmap\/hashmap-changes-in-java-8\/<\/p>\n
http:\/\/javahungry.blogspot.com\/2013\/08\/hashing-how-hash-map-works-in-java-or.html<\/p>\n
http:\/\/sinhvienit.net\/forum\/hashmap-trong-java.353561.html<\/p>\n
http:\/\/www.tutorialspoint.com\/java\/java_hashmap_class.htm<\/p>","protected":false},"excerpt":{"rendered":"
Gi\u1edbi thi\u1ec7u HashMap l\u00e0 l\u1edbp s\u1eed d\u1ee5ng m\u1ed9t b\u1ea3ng b\u0103m \u0111\u1ec3 c\u00e0i \u0111\u1eb7t m\u1ed9t ki\u1ec3u d\u1eef li\u1ec7u t\u1eeb\u00a0giao di\u1ec7n Map (Map interface). N\u00f3 gi\u1ea3m th\u1eddi gian th\u1ef1c hi\u1ec7n c\u00e1c ph\u00e9p… <\/p>\n","protected":false},"author":2,"featured_media":2675,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,10],"tags":[624,625],"class_list":["post-2071","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java","category-java-techs","tag-hashmap","tag-map"],"_links":{"self":[{"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/posts\/2071","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/comments?post=2071"}],"version-history":[{"count":29,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/posts\/2071\/revisions"}],"predecessor-version":[{"id":2679,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/posts\/2071\/revisions\/2679"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/media\/2675"}],"wp:attachment":[{"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/media?parent=2071"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/categories?post=2071"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.itersdesktop.com\/vi\/wp-json\/wp\/v2\/tags?post=2071"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}