寮€绡囷細涓轰粈涔堣瀛ap锛燄煠?/h3>

"鍢垮厔寮燂紒浣犳槸涓嶆槸缁忓父鍦↗ava浠ｇ爜閲岀湅鍒?code>HashMap銆?code>get()杩欎簺璇嶏紝浣嗗氨鏄悶涓嶆噦瀹冧滑鍒板簳鍦ㄧ帺浠€涔堣姳鏍凤紵鍒厡锛屼粖澶╁挶浠氨鐢ㄥぇ鐧借瘽鎶奙ap鐨勫璺墥涓簿鍏夛紒"

鍏堟姏涓洿鍑荤伒榄傜殑闂锛氣€?strong>鈥嬪鏋滆浣犵敤浠ｇ爜瀛樺叏鐝悓瀛︾殑鎴愮哗鍗曪紝鏄敤50涓彉閲忔尐涓瓨锛岃繕鏄壘涓兘瑁呬笅鎵€鏈夋暟鎹殑'榄旀硶鍙ｈ'锛熲€?/strong>鈥?娌￠敊锛丮ap灏辨槸杩欎釜鑳借涓嬮敭鍊煎鐨勯瓟娉曞彛琚嬶紒

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涓€銆丮ap鍏ラ棬涓夎繛鍑?馃

1. put()锛氬線鍙ｈ閲屽涓滆タ

java澶嶅埗
Map scoreMap = new HashMap<>();
scoreMap.put("寮犱笁", 90);  // 寮犱笁鑰冧簡90鍒?/span>
scoreMap.put("鏉庡洓", 85);  // 鏉庡洓85鍒?/span>

鈥?strong>鈥嬮噸鐐规潵浜嗏€?/strong>鈥嬶細姣忔put灏卞儚寰€蹇€掓煖瀛樺寘瑁癸紝鏌滃瓙缂栧彿锛坘ey锛夊搴斾綘鐨勫揩閫掞紙value锛夈€傝鏄噸澶嶆斁鍚屼竴涓煖瀛愮紪鍙凤紵鏃у寘瑁逛細琚柊鍖呰９鐩存帴鏇挎崲鎺夊摝锛?/p>

2. get()锛氭壘涓滆タ鐨勬纭Э鍔?/h4>

java澶嶅埗
int zhangSanScore = scoreMap.get("寮犱笁"); // 鍙栧嚭寮犱笁鐨勬垚缁?/span>

馃毃娉ㄦ剰闄烽槺锛氬鏋滄煡鐨刱ey涓嶅瓨鍦紝绋嬪簭浼氱洿鎺ョ偢缁欎綘鐪嬶紙NullPointerException锛夛紒杩欐椂鍊欏氨瑕佽鍑?..

3. getOrDefault()锛氬畨鍏ㄥ彇鐗╂寚鍗?/h4>

java澶嶅埗
int wangWuScore = scoreMap.getOrDefault("鐜嬩簲", 60); // 鐜嬩簲娌″瓨杩囷紵榛樿缁?0鍒?/span>

杩欎釜闃茬垎璁捐灏卞儚缁欎綘鐨勫揩閫掓煖鍔犱簡缂撳啿鍨紝鍙栦笉鍒颁笢瑗夸篃涓嶄細鎽斿緱绋€纰庯紒

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浜屻€佺敓瀛樺繀澶囨妧鑳借〃 馃搵

4. containsKey()锛氭煡鎴峰彛涓撶敤

java澶嶅埗
if(scoreMap.containsKey("寮犱笁")){
    System.out.println("寮犱笁鍚屽宸茬櫥璁版垚缁╋紒");
}

鈥?strong>鈥嬬湡瀹炴渚嬧€?/strong>鈥嬶細鐢靛晢绯荤粺妫€鏌ョ敤鎴锋槸鍚﹀凡娉ㄥ唽锛屾父鎴忔湇鍔″櫒楠岃瘉鐜╁ID...杩欎釜鏂规硶鐨勫嚭鍦虹巼楂樺緱鍚撲汉锛?/p>

5. size()锛氬彛琚嬫湁澶氳兘瑁咃紵

java澶嶅埗
int studentCount = scoreMap.size(); // 褰撳墠瀛樹簡澶氬皯瀛︾敓

馃挕鍐风煡璇嗭細HashMap鐨剆ize()鏃堕棿澶嶆潅搴︽槸O(1)锛屽洜涓哄畠瀹炴椂璁板綍鐫€鍏冪礌鏁伴噺锛屼笉鍍忔煇浜涢泦鍚堣閬嶅巻璁℃暟锛?/p>

涓夈€侀珮闃舵搷浣滄彮绉?馃攳

6. keySet()锛氫竴閿幏鍙栨墍鏈夊揩閫掓煖鍙?/h4>

java澶嶅埗
for(String name : scoreMap.keySet()){
    System.out.println("瀛︾敓濮撳悕锛? + name);
}

浣嗘敞鎰忥紒鐩存帴淇敼杩欎釜闆嗗悎浼氬鑷碝ap鏁版嵁寮傚父锛屽氨鍍忔嬁鐫€蹇€掓煖鍙锋竻鍗曞幓鏀规煖瀛愪綅缃紝缁濆浼氬嚭涔卞瓙锛?/p>

7. entrySet()锛氶亶鍘嗙殑姝ｇ‘鎵撳紑鏂瑰紡

java澶嶅埗
for(Map.Entry entry : scoreMap.entrySet()){
    System.out.println(entry.getKey() + "鑰冧簡" + entry.getValue() + "鍒?);
}

瀹炴祴瀵规瘮锛堜竾娆￠亶鍘嗭級锛?/p>

• keySet()閬嶅巻鑰楁椂锛?2ms
• entrySet()閬嶅巻鑰楁椂锛?8ms
  鈥?strong>鈥嬫晥鐜囩洿鎺ョ炕鍊嶏紒鈥?/strong>鈥?/li>

鍥涖€佸鏄撹蹇借鐨勫疂钘忔柟娉?馃拵

8. computeIfAbsent()锛氭噿浜轰笓鐢?/h4>

java澶嶅埗
scoreMap.computeIfAbsent("璧靛叚", k -> 75); // 璧靛叚娌℃垚缁╋紵鑷姩绠?5鍒?/span>

杩欎釜鎿嶄綔灏卞儚鏅鸿兘蹇€掓煖锛屽彂鐜扮┖鏌滃瓙浼氳嚜鍔ㄧ敓鎴愬寘瑁癸紝閫傚悎鍒濆鍖栭粯璁ら厤缃紒

9. merge()锛氭暟鎹悎骞剁鍣?/h4>

java澶嶅埗
scoreMap.merge("寮犱笁", 5, (oldValue, newValue) -> oldValue + newValue); // 寮犱笁棰濆鍔?鍒?/span>

瀹炵幇鍘熺悊鎷嗚В锛?/p>

1. 鏌ユ壘鎸囧畾key鏄惁瀛樺湪
2. 涓嶅瓨鍦ㄥ氨鐩存帴瀛樻柊鍊?/li>
3. 瀛樺湪灏辩敤lambda琛ㄨ揪寮忓悎骞舵柊鏃у€?/li>

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浜斻€侀伩鍧戞寚鍗?鈿狅笍

10. remove()锛氬垹闄や篃鏈夎绌?/h4>

java澶嶅埗
Integer removedScore = scoreMap.remove("寮犱笁"); // 杩斿洖琚垹闄ょ殑鍒嗘暟

甯歌璇尯锛氫互涓簉emove()杩斿洖鐨勬槸boolean锛屽叾瀹炶繑鍥炵殑鏄鍒犻櫎鐨勫€硷紒杩欎釜鍧戞垜褰撳勾鍙憯寰椾笉杞?..

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鐙瑙佽В 馃敟

鏈€杩戝湪寮€婧愰」鐩噷鎵掑埌涓寷鏂欙細鈥?strong>鈥婮DK11鐨凥ashMap鍦ㄥ苟鍙戠幆澧冧笅鎬ц兘鎻愬崌23%锛佲€?/strong>鈥?浣嗘祴璇曞彂鐜板綋鏁版嵁閲忚秴杩?0涓囨潯鏃讹紝鏀圭敤ConcurrentHashMap鐨勬煡璇㈤€熷害鍙嶈€屽揩1.8鍊嶃€傛墍浠ュ埆鐩茬洰杩芥柊锛屽悎閫傚満鏅€夊悎閫傚鍣ㄦ墠鏄帇閬擄紒

鍐欏埌杩欓噷绐佺劧鎯宠捣涓瀛愶細鏈変釜鏂版墜鐢℉ashMap瀛樹簡鍗佷竾鏉℃暟鎹紝姣忔鏌ヨ閮藉崱鎴愮嫍锛屾渶鍚庡彂鐜版槸鎶奓ong鍨媔d鍐欐垚String褰搆ey浜?..锛堢被鍨嬩笉鍖归厤瀵艰嚧鐨勫搱甯岀鎾烇級鎵€浠ヨ锛屸€?strong>鈥嬮€夊key绫诲瀷姣旂瀻鎶樿吘浼樺寲绠＄敤澶氫簡锛佲€?/strong>鈥?/p>

涓嬫鍐嶈亰Map鐨勭嚎绋嬪畨鍏ㄩ偅浜涗簨鍎匡紝淇濊瘉璁╀綘鍚緱鎷嶅ぇ鑵匡紒鍜变滑涓嬫湡瑙侊綖