{"id":26081,"date":"2023-04-24T12:08:42","date_gmt":"2023-04-24T04:08:42","guid":{"rendered":"https:\/\/docs.pingcode.com\/?p=26081"},"modified":"2023-07-30T23:29:32","modified_gmt":"2023-07-30T15:29:32","slug":"%e6%95%b0%e6%8d%ae%e7%bb%93%e6%9e%84%e4%b8%adhashmap%e4%b8%8ehashtable%e7%9a%84%e5%8c%ba%e5%88%ab%e6%98%af%e4%bb%80%e4%b9%88","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/26081.html","title":{"rendered":"\u6570\u636e\u7ed3\u6784\u4e2dHashMap\u4e0eHashTable\u7684\u533a\u522b\u662f\u4ec0\u4e48"},"content":{"rendered":"
\n

\u6570\u636e\u7ed3\u6784\u4e2dHashMap\u4e0eHashTable\u7684\u533a\u522b\u662f\uff1a1\u3001\u7ee7\u627f\u7684\u7236\u7c7b\u4e0d\u540c\uff1b2\u3001\u7ebf\u7a0b\u5b89\u5168\u6027\u4e0d\u540c\uff1b3\u3001\u662f\u5426\u63d0\u4f9bcontains\u65b9\u6cd5\uff1b4\u3001key\u548cvalue\u662f\u5426\u5141\u8bb8null\u503c\uff1b5\u3001\u4e24\u4e2a\u904d\u5386\u65b9\u5f0f\u7684\u5185\u90e8\u5b9e\u73b0\u4e0a\u4e0d\u540c\uff1b6\u3001hash\u503c\u4e0d\u540c\u7b49\u3002<\/p>\n<\/blockquote>\n

\n
\"\"<\/figure>\n<\/div>\n

\u4e00\u3001\u6570\u636e\u7ed3\u6784\u4e2dHashMap\u4e0eHashTable\u7684\u533a\u522b<\/strong><\/h2>\n

1<\/strong>\u3001\u7ee7\u627f\u7684\u7236\u7c7b\u4e0d\u540c<\/strong><\/h3>\n

Hashtable\u7ee7\u627f\u81eaDictionary\u7c7b\uff0c\u800cHashMap\u7ee7\u627f\u81eaAbstractMap\u7c7b\u3002\u4f46\u4e8c\u8005\u90fd\u5b9e\u73b0\u4e86Map\u63a5\u53e3\u3002<\/p>\n

<\/a>2<\/strong>\u3001\u7ebf\u7a0b\u5b89\u5168\u6027\u4e0d\u540c<\/strong><\/h3>\n

javadoc\u4e2d\u5173\u4e8ehashmap\u7684\u4e00\u6bb5\u63cf\u8ff0\u5982\u4e0b\uff1a\u6b64\u5b9e\u73b0\u4e0d\u662f\u540c\u6b65\u7684\u3002\u5982\u679c\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u8bbf\u95ee\u4e00\u4e2a\u54c8\u5e0c\u6620\u5c04\uff0c\u800c\u5176\u4e2d\u81f3\u5c11\u4e00\u4e2a\u7ebf\u7a0b\u4ece\u7ed3\u6784\u4e0a\u4fee\u6539\u4e86\u8be5\u6620\u5c04\uff0c\u5219\u5b83\u5fc5\u987b\u4fdd\u6301\u5916\u90e8\u540c\u6b65\u3002Hashtable \u4e2d\u7684\u65b9\u6cd5\u662fSynchronize\u7684\uff0c\u800cHashMap\u4e2d\u7684\u65b9\u6cd5\u5728\u7f3a\u7701\u60c5\u51b5\u4e0b\u662f\u975eSynchronize\u7684\u3002\u5728\u591a\u7ebf\u7a0b\u5e76\u53d1\u7684\u73af\u5883\u4e0b\uff0c\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528Hashtable\uff0c\u4e0d\u9700\u8981\u81ea\u5df1\u4e3a\u5b83\u7684\u65b9\u6cd5\u5b9e\u73b0\u540c\u6b65\uff0c\u4f46\u4f7f\u7528HashMap\u65f6\u5c31\u5fc5\u987b\u8981\u81ea\u5df1\u589e\u52a0\u540c\u6b65\u5904\u7406\u3002\uff08\u7ed3\u6784\u4e0a\u7684\u4fee\u6539\u662f\u6307\u6dfb\u52a0\u6216\u5220\u9664\u4e00\u4e2a\u6216\u591a\u4e2a\u6620\u5c04\u5173\u7cfb\u7684\u4efb\u4f55\u64cd\u4f5c\uff1b\u4ec5\u6539\u53d8\u4e0e\u5b9e\u4f8b\u5df2\u7ecf\u5305\u542b\u7684\u952e\u5173\u8054\u7684\u503c\u4e0d\u662f\u7ed3\u6784\u4e0a\u7684\u4fee\u6539\u3002\uff09\u8fd9\u4e00\u822c\u901a\u8fc7\u5bf9\u81ea\u7136\u5c01\u88c5\u8be5\u6620\u5c04\u7684\u5bf9\u8c61\u8fdb\u884c\u540c\u6b65\u64cd\u4f5c\u6765\u5b8c\u6210\u3002\u5982\u679c\u4e0d\u5b58\u5728\u8fd9\u6837\u7684\u5bf9\u8c61\uff0c\u5219\u5e94\u8be5\u4f7f\u7528\u00a0Collections.synchronizedMap\u00a0\u65b9\u6cd5\u6765\u201c\u5305\u88c5\u201d\u8be5\u6620\u5c04\u3002\u8f83\u597d\u5728\u521b\u5efa\u65f6\u5b8c\u6210\u8fd9\u4e00\u64cd\u4f5c\uff0c\u4ee5\u9632\u6b62\u5bf9\u6620\u5c04\u8fdb\u884c\u610f\u5916\u7684\u975e\u540c\u6b65\u8bbf\u95ee\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n

Map m = Collections.synchronizedMap(new HashMap(\u2026));<\/p>\n

Hashtable \u7ebf\u7a0b\u5b89\u5168\u5f88\u597d\u7406\u89e3\uff0c\u56e0\u4e3a\u5b83\u6bcf\u4e2a\u65b9\u6cd5\u4e2d\u90fd\u52a0\u5165\u4e86Synchronize\u3002<\/p>\n

<\/a>3<\/strong>\u3001\u662f\u5426\u63d0\u4f9bcontains\u65b9\u6cd5<\/strong><\/h3>\n

HashMap\u628aHashtable\u7684contains\u65b9\u6cd5\u53bb\u6389\u4e86\uff0c\u6539\u6210containsValue\u548ccontainsKey\uff0c\u56e0\u4e3acontains\u65b9\u6cd5\u5bb9\u6613\u8ba9\u4eba\u5f15\u8d77\u8bef\u89e3\u3002<\/p>\n

Hashtable\u5219\u4fdd\u7559\u4e86contains\uff0ccontainsValue\u548ccontainsKey\u4e09\u4e2a\u65b9\u6cd5\uff0c\u5176\u4e2dcontains\u548ccontainsValue\u529f\u80fd\u76f8\u540c\u3002<\/p>\n

<\/a>4<\/strong>\u3001key\u548cvalue\u662f\u5426\u5141\u8bb8null\u503c<\/strong><\/h3>\n

Hashtable\u4e2d\uff0ckey\u548cvalue\u90fd\u4e0d\u5141\u8bb8\u51fa\u73b0null\u503c\u3002<\/p>\n

\u56e0\u4e3ahashtable,concurrenthashmap\u5b83\u4eec\u662f\u7528\u4e8e\u591a\u7ebf\u7a0b\u7684\uff0c\u5e76\u53d1\u7684 \uff0c\u5982\u679cmap.get(key)\u5f97\u5230\u4e86null\uff0c\u4e0d\u80fd\u5224\u65ad\u5230\u5e95\u662f\u6620\u5c04\u7684value\u662fnull,\u8fd8\u662f\u56e0\u4e3a\u6ca1\u6709\u627e\u5230\u5bf9\u5e94\u7684key\u800c\u4e3a\u7a7a\uff0c\u800c\u7528\u4e8e\u5355\u7ebf\u7a0b\u72b6\u6001\u7684hashmap\u5374\u53ef\u4ee5\u7528containKey\uff08key\uff09 \u53bb\u5224\u65ad\u5230\u5e95\u662f\u5426\u5305\u542b\u4e86\u8fd9\u4e2anull\u3002<\/p>\n

hashtable\u4e3a\u4ec0\u4e48\u5c31\u4e0d\u80fdcontainKey(key)
\u4e00\u4e2a\u7ebf\u7a0b\u5148get(key)\u518dcontainKey(key)\uff0c\u8fd9\u4e24\u4e2a\u65b9\u6cd5\u7684\u4e2d\u95f4\u65f6\u523b\uff0c\u5176\u4ed6\u7ebf\u7a0b\u600e\u4e48\u64cd\u4f5c\u8fd9\u4e2akey\u90fd\u4f1a\u53ef\u80fd\u53d1\u751f\uff0c\u4f8b\u5982\u5220\u6389\u8fd9\u4e2akey<\/p>\n

<\/a>5<\/strong>\u3001\u4e24\u4e2a\u904d\u5386\u65b9\u5f0f\u7684\u5185\u90e8\u5b9e\u73b0\u4e0a\u4e0d\u540c<\/strong><\/h3>\n

Hashtable\u3001HashMap\u90fd\u4f7f\u7528\u4e86 Iterator\u3002\u800c\u7531\u4e8e\u5386\u53f2\u539f\u56e0\uff0cHashtable\u8fd8\u4f7f\u7528\u4e86Enumeration\u7684\u65b9\u5f0f \u3002<\/p>\n

<\/a>6<\/strong>\u3001hash\u503c\u4e0d\u540c<\/strong><\/h3>\n

\u54c8\u5e0c\u503c\u7684\u4f7f\u7528\u4e0d\u540c\uff0cHashTable\u76f4\u63a5\u4f7f\u7528\u5bf9\u8c61\u7684hashCode\u3002\u800cHashMap\u91cd\u65b0\u8ba1\u7b97hash\u503c\u3002<\/p>\n

hashCode\u662fjdk\u6839\u636e\u5bf9\u8c61\u7684\u5730\u5740\u6216\u8005\u5b57\u7b26\u4e32\u6216\u8005\u6570\u5b57\u7b97\u51fa\u6765\u7684int\u7c7b\u578b\u7684\u6570\u503c\u3002<\/p>\n

Hashtable\u8ba1\u7b97hash\u503c\uff0c\u76f4\u63a5\u7528key\u7684hashCode()\uff0c\u800cHashMap\u91cd\u65b0\u8ba1\u7b97\u4e86key\u7684hash\u503c\uff0cHashtable\u5728\u6c42hash\u503c\u5bf9\u5e94\u7684\u4f4d\u7f6e\u7d22\u5f15\u65f6\uff0c\u7528\u53d6\u6a21\u8fd0\u7b97\uff0c\u800cHashMap\u5728\u6c42\u4f4d\u7f6e\u7d22\u5f15\u65f6\uff0c\u5219\u7528\u4e0e\u8fd0\u7b97\uff0c\u4e14\u8fd9\u91cc\u4e00\u822c\u5148\u7528hash&0x7FFFFFFF\u540e\uff0c\u518d\u5bf9length\u53d6\u6a21\uff0c&0x7FFFFFFF\u7684\u76ee\u7684\u662f\u4e3a\u4e86\u5c06\u8d1f\u7684hash\u503c\u8f6c\u5316\u4e3a\u6b63\u503c\uff0c\u56e0\u4e3ahash\u503c\u6709\u53ef\u80fd\u4e3a\u8d1f\u6570\uff0c\u800c&0x7FFFFFFF\u540e\uff0c\u53ea\u6709\u7b26\u53f7\u5916\u6539\u53d8\uff0c\u800c\u540e\u9762\u7684\u4f4d\u90fd\u4e0d\u53d8\u3002<\/p>\n

<\/a>7<\/strong>\u3001\u5185\u90e8\u5b9e\u73b0\u4f7f\u7528\u7684\u6570\u7ec4\u521d\u59cb\u5316\u548c\u6269\u5bb9\u65b9\u5f0f\u4e0d\u540c<\/strong><\/h3>\n

HashTable\u5728\u4e0d\u6307\u5b9a\u5bb9\u91cf\u7684\u60c5\u51b5\u4e0b\u7684\u9ed8\u8ba4\u5bb9\u91cf\u4e3a11\uff0c\u800cHashMap\u4e3a16\uff0cHashtable\u4e0d\u8981\u6c42\u5e95\u5c42\u6570\u7ec4\u7684\u5bb9\u91cf\u4e00\u5b9a\u8981\u4e3a2\u7684\u6574\u6570\u6b21\u5e42\uff0c\u800cHashMap\u5219\u8981\u6c42\u4e00\u5b9a\u4e3a2\u7684\u6574\u6570\u6b21\u5e42\u3002
Hashtable\u6269\u5bb9\u65f6\uff0c\u5c06\u5bb9\u91cf\u53d8\u4e3a\u539f\u6765\u76842\u500d\u52a01\uff0c\u800cHashMap\u6269\u5bb9\u65f6\uff0c\u5c06\u5bb9\u91cf\u53d8\u4e3a\u539f\u6765\u76842\u500d\u3002<\/p>\n

Hashtable\u548cHashMap\u5b83\u4eec\u4e24\u4e2a\u5185\u90e8\u5b9e\u73b0\u65b9\u5f0f\u7684\u6570\u7ec4\u7684\u521d\u59cb\u5927\u5c0f\u548c\u6269\u5bb9\u7684\u65b9\u5f0f\u3002HashTable\u4e2dhash\u6570\u7ec4\u9ed8\u8ba4\u5927\u5c0f\u662f11\uff0c\u589e\u52a0\u7684\u65b9\u5f0f\u662f old*2+1\u3002<\/p>\n

\u5ef6\u4f38\u9605\u8bfb\uff1a<\/strong><\/p>\n

\u4e8c\u3001HashMap\u7b80\u4ecb<\/strong><\/h3>\n

HashMap\u662f\u57fa\u4e8e\u54c8\u5e0c\u8868\u5b9e\u73b0\u7684\uff0c\u6bcf\u4e00\u4e2a\u5143\u7d20\u662f\u4e00\u4e2akey-value\u5bf9\uff0c\u5176\u5185\u90e8\u901a\u8fc7\u5355\u94fe\u8868\u89e3\u51b3\u51b2\u7a81\u95ee\u9898\uff0c\u5bb9\u91cf\u4e0d\u8db3\uff08\u8d85\u8fc7\u4e86\u9600\u503c\uff09\u65f6\uff0c\u540c\u6837\u4f1a\u81ea\u52a8\u589e\u957f\u3002<\/p>\n

HashMap\u662f\u975e\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u53ea\u662f\u7528\u4e8e\u5355\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\u53ef\u4ee5\u91c7\u7528concurrent\u5e76\u53d1\u5305\u4e0b\u7684concurrentHashMap\u3002<\/p>\n

HashMap \u5b9e\u73b0\u4e86Serializable\u63a5\u53e3\uff0c\u56e0\u6b64\u5b83\u652f\u6301\u5e8f\u5217\u5316\uff0c\u5b9e\u73b0\u4e86Cloneable\u63a5\u53e3\uff0c\u80fd\u88ab\u514b\u9686\u3002<\/p>\n

HashMap\u5b58\u6570\u636e\u7684\u8fc7\u7a0b\u662f\uff1a<\/p>\n

HashMap\u5185\u90e8\u7ef4\u62a4\u4e86\u4e00\u4e2a\u5b58\u50a8\u6570\u636e\u7684Entry\u6570\u7ec4\uff0cHashMap\u91c7\u7528\u94fe\u8868\u89e3\u51b3\u51b2\u7a81\uff0c\u6bcf\u4e00\u4e2aEntry\u672c\u8d28\u4e0a\u662f\u4e00\u4e2a\u5355\u5411\u94fe\u8868\u3002\u5f53\u51c6\u5907\u6dfb\u52a0\u4e00\u4e2akey-value\u5bf9\u65f6\uff0c\u9996\u5148\u901a\u8fc7hash(key)\u65b9\u6cd5\u8ba1\u7b97hash\u503c\uff0c\u7136\u540e\u901a\u8fc7indexFor(hash,length)\u6c42\u8be5key-value\u5bf9\u7684\u5b58\u50a8\u4f4d\u7f6e\uff0c\u8ba1\u7b97\u65b9\u6cd5\u662f\u5148\u7528hash&0x7FFFFFFF\u540e\uff0c\u518d\u5bf9length\u53d6\u6a21\uff0c\u8fd9\u5c31\u4fdd\u8bc1\u6bcf\u4e00\u4e2akey-value\u5bf9\u90fd\u80fd\u5b58\u5165HashMap\u4e2d\uff0c\u5f53\u8ba1\u7b97\u51fa\u7684\u4f4d\u7f6e\u76f8\u540c\u65f6\uff0c\u7531\u4e8e\u5b58\u5165\u4f4d\u7f6e\u662f\u4e00\u4e2a\u94fe\u8868\uff0c\u5219\u628a\u8fd9\u4e2akey-value\u5bf9\u63d2\u5165\u94fe\u8868\u5934\u3002<\/p>\n

HashMap\u4e2dkey\u548cvalue\u90fd\u5141\u8bb8\u4e3anull\u3002key\u4e3anull\u7684\u952e\u503c\u5bf9\u6c38\u8fdc\u90fd\u653e\u5728\u4ee5table[0]\u4e3a\u5934\u7ed3\u70b9\u7684\u94fe\u8868\u4e2d\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"\u6570\u636e\u7ed3\u6784\u4e2dHashMap\u4e0eHashTable\u7684\u533a\u522b\u662f\uff1a1\u3001\u7ee7\u627f\u7684\u7236\u7c7b\u4e0d\u540c\uff1b2\u3001\u7ebf\u7a0b\u5b89\u5168\u6027\u4e0d\u540c\uff1b3\u3001\u662f\u5426\u63d0\u4f9bco […]","protected":false},"author":1,"featured_media":26082,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[37],"tags":[],"acf":[],"_links":{"self":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/26081"}],"collection":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/comments?post=26081"}],"version-history":[{"count":0,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/26081\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media\/26082"}],"wp:attachment":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media?parent=26081"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/categories?post=26081"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/tags?post=26081"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}