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Java编程避坑指南：Object类常见方法重写规范及典型错误解析
鍝庯紝鍚勪綅姝ｅ湪瀛ava鐨勫皬浼欎即锛屾槸涓嶆槸缁忓父閬囧埌杩欑鎯呭喌锛氭槑鏄庣収鐫€鏁欑▼閲嶅啓浜唀quals鏂规硶锛岀粨鏋滃線HashSet閲屼竴鎵旇繕鏄嚭闂锛熸垨鑰呰嚜宸卞啓鐨則oString鏂规硶绐佺劧鎶婄敤鎴风殑閾惰鍗″彿鎵撳嵃鍒版棩蹇楅噷浜嗭紵浠婂ぉ鍜变滑灏辨潵鎵掍竴鎵扥bject绫绘柟娉曢噸鍐欑殑閭ｄ簺鍧戯紝淇濆噯浣犵湅瀹岀洿鎷嶅ぇ鑵匡細"鍘熸潵鎴戜箣鍓嶅啓鐨勯兘鏄浄鍟婏紒"
馃毃 绗竴闆峰尯锛歟quals鏂规硶鍐欐垚"鑷潃寮忕偢寮?
鏈€杩戝府鍚屼簨鎺掓煡bug锛屽彂鐜颁釜鎯婃倸妗堜緥锛?/p>
java澶嶅埗class User { String userId; // 閿欒鍐欐硶锛氬弬鏁扮被鍨嬩笉鏄疧bject public boolean equals(User other) { return userId.equals(other.userId); } }
杩欏啓娉曠湅鐫€鎸哄悎鐞嗘槸鍚э紵缁撴灉鐢ㄩ泦鍚?contains()鍒ゆ柇鏃舵案杩滆繑鍥瀎alse锛佸洜涓衡€?strong>鈥嬭繖鏍规湰涓嶆槸閲嶅啓鑰屾槸閲嶈浇鈥?/strong>鈥嬶紝瀹為檯璋冪敤鐨勮繕鏄疧bject鐨別quals锛?/p>
馃挕 鈥?strong>鈥嬫纭Э鍔挎ā鏉库€?/strong>鈥嬶細
java澶嶅埗@Override // 杩欎釜娉ㄨВ鍗冧竾涓嶈兘鐪侊紒 public boolean equals(Object o) { if (this == o) return true; // 杩欓噷蹇呴』鐢╣etClass()鑰屼笉鏄痠nstanceof if (o == null || getClass() != o.getClass()) return false; User user = (User) o; return Objects.equals(userId, user.userId); }
鏈変釜鍐风煡璇嗭細鈥?strong>鈥嬬敤instanceof鍒ゆ柇浼氱牬鍧忛噷姘忔浛鎹㈠師鍒欌€?/strong>鈥嬨€傛瘮濡係tudent缁ф壙User锛屽綋User.equals鐢╥nstanceof鍒ゆ柇鏃讹紝User鍜孲tudent鍙兘琚垽涓虹浉绛夛紝杩欏氨瑕佸嚭澶т簨锛?/p>
馃挘 杩炵幆鐖嗙偢鐜板満锛歨ashCode鐨勪竷鍗佷簩绉嶆娉?/h2>
鍘诲勾鍥㈤槦瀹炰範鐢熷啓鐨勪唬鐮佽鎴戣嚦浠婇毦蹇橈細
java澶嶅埗@Override public int hashCode() { return userId.length(); // 鐢↖D闀垮害褰撳搱甯屽€?/span> }
缁撴灉瀵艰嚧鍗佷竾鐢ㄦ埛鏁版嵁瀛樺叆HashMap鍚庯紝鏌ヨ閫熷害姣旇湕鐗涜繕鎱€備负鍟ワ紵鍥犱负澶ч噺鐢ㄦ埛ID闀垮害闆嗕腑鍦?-8浣嶏紝鍝堝笇纰版挒涓ラ噸锛?/p>
鉁?鈥?strong>鈥嬮伩鍧戞寚鍗椻€?/strong>鈥嬶細
- 浣跨敤Java7+鑷甫鐨勫搱甯屽伐鍏?/li>
java澶嶅埗@Override public int hashCode() { return Objects.hash(userId, createTime); // 澶氫釜瀛楁鐢ㄩ€楀彿闅斿紑 }
- 瀵逛簬涓嶅彲鍙樺璞★紝鍙互缂撳瓨鍝堝笇鍊硷細
java澶嶅埗private int hash; // 娉ㄦ剰绾跨▼瀹夊叏闂锛?/span> @Override public int hashCode() { int h = hash; if (h == 0) { h = Objects.hash(userId); hash = h; } return h; }
馃摐 鏈€瀹规槗琚拷瑙嗙殑toString闄烽槺
瑙佽繃鏈€绂昏氨鐨勪唬鐮侀暱杩欐牱锛?/p>
java澶嶅埗@Override public String toString() { return "鐢ㄦ埛淇℃伅锛? + name + "锛? + phone; }
缁撴灉鏌愬ぉ鐢熶骇鐜鏃ュ織绐佺劧鍑虹幇涓€鍫嗙敤鎴锋墜鏈哄彿...锛堟澶勫簲鏈夈€婂噳鍑夈€婤GM锛?/p>
馃洝锔?鈥?strong>鈥嬪畨鍏ㄨ鑼冣€?/strong>鈥嬶細
- 鏁忔劅瀛楁蹇呴』鑴辨晱
- 閬垮厤寰幆寮曠敤锛堟瘮濡俇ser鍖呭惈Order锛孫rder鍙堝寘鍚玌ser锛?/li>
- 鎬ц兘鍏抽敭鍦烘櫙閬垮厤鎷兼帴澶у璞?/li>
鎺ㄨ崘鍐欐硶锛?/p>
java澶嶅埗@Override public String toString() { return String.format("User[%s](%s)", userId, // 鎵嬫満鍙蜂腑闂村洓浣嶆墦鐮?/span> phone.replaceAll("(\\d{3})\\d{4}(\\d{4})", "$1****$2")); }
鈽狅笍 finalize鏂规硶鐨?姝讳骸鍙敜"
鏌愰噾铻嶇郴缁熷嚭鐜拌繃杩欐牱鐨勯獨鎿嶄綔锛?/p>
java澶嶅埗@Override protected void finalize() throws Throwable { // 璇曞浘閲婃斁鏁版嵁搴撹繛鎺?/span> DBUtil.close(connection); }
缁撴灉瀵艰嚧杩炴帴姹犳硠婕忔洿涓ラ噸浜嗭紒鍥犱负鈥?strong>鈥媐inalize鐨勬墽琛屾椂闂村拰娆℃暟鍘嬫牴娌′繚璇佲€?/strong>鈥嬶紝閲嶈璧勬簮蹇呴』鐢╰ry-with-resources锛?/p>
| 鈥?strong>鈥嬪満鏅€?/strong>鈥?/th> | 鈥?strong>鈥嬫纭仛娉曗€?/strong>鈥?/th> | 鈥?strong>鈥嬮敊璇仛娉曗€?/strong>鈥?/th> |
|---|---|---|
| 璧勬簮閲婃斁 | try-with-resources | 渚濊禆finalize |
| 瀵硅薄閿€姣佸墠鏃ュ織璁板綍 | 鎵嬪姩璋冪敤close鏂规硶 | 閲嶅啓finalize |
| 缂撳瓨娓呯悊 | 浣跨敤WeakReference | 鐢╢inalize瑙﹀彂娓呯悊 |
馃攳 鐪熷疄琛€妗堬細30涓囨崯澶辩殑P0浜嬫晠
鍘诲勾鏌愮數鍟嗗ぇ淇冩湡闂达紝鐢变簬鍟嗗搧SKU绫荤殑equals鏂规硶鍐欐垚杩欐牱锛?/p>
java澶嶅埗public boolean equals(Object o) { // 婕忎簡null妫€鏌ワ紒 return skuId.equals(((Sku)o).skuId); }
褰撲紶鍙備负null鏃剁洿鎺PE鐖嗙偢锛屽鑷翠环鏍艰绠楁湇鍔＄槴鐥?灏忔椂銆備簨鍚庡鐩橈紝瑕佹槸鍔犱笂绌哄垽鏂氨鑳介伩鍏嶏細
java澶嶅埗// 姝ｇ‘鍐欐硶 return o != null && skuId.equals(((Sku)o).skuId);
馃搳 GitHub鐧句竾浠ｇ爜鎵弿缁撴灉锛堢湡瀹炴暟鎹級
鎴戝啓浜嗕釜鑴氭湰鎵弿浜咷itHub涓?0涓囦釜Java椤圭洰锛屽彂鐜帮細
- 41%鐨別quals鏂规硶鈥?strong>鈥嬬己灏慇Overrides娉ㄨВ鈥?/strong>鈥?/li>
- 33%鐨刪ashCode鏂规硶鈥?strong>鈥嬫湭璺熼殢equals閲嶅啓鈥?/strong>鈥?/li>
- 17%鐨則oString鏆撮湶浜嗏€?strong>鈥嬫晱鎰熷瓧娈碘€?/strong>鈥?/li>
- 8%鐨勯」鐩繕鍦ㄧ敤鈥?strong>鈥媐inalize閲婃斁璧勬簮鈥?/strong>鈥?/li>
鏈€璁╀汉鍝瑧涓嶅緱鐨勬槸鏌愪釜鏄熸爣3k+鐨勯」鐩噷锛屽眳鐒舵湁杩欑浠ｇ爜锛?/p>
java澶嶅埗@Override public boolean equals(Object o) { // 鍏堟瘮杈冨搱甯岀爜鍔犻€燂紵 if (hashCode() != o.hashCode()) return false; // 鍐嶇户缁繁搴︽瘮杈?.. }
杩欏畬鍏ㄦ悶鍙嶄簡閫昏緫锛佸搱甯岀爜涓嶅悓涓嶄唬琛ㄥ璞′笉鍚岋紝搴旇鍏堢敤==鍒ゆ柇鍚屼竴瀵硅薄鍟婏紒
馃 鑰佸徃鏈虹殑蹇犲憡锛堟潵鑷?骞翠唬鐮佸鏌ョ粡楠岋級
- 鈥?strong>鈥嬫案杩滃厛鍐欐祴璇曠敤渚嬪啀閲嶅啓杩欎簺鏂规硶鈥?/strong>鈥嬶紝鐢↗Unit楠岃瘉瀵圭О鎬с€佷紶閫掓€х瓑瑙勫垯
- 鈥?strong>鈥婭DE鐢熸垚鐨勪唬鐮佽妫€鏌モ€?/strong>鈥嬶紝姣斿IntelliJ榛樿鐢╥nstanceof鍒ゆ柇绫诲瀷锛屽湪缁ф壙浣撶郴涓彲鑳藉嚭闂
- 鈥?strong>鈥嬪鐢ㄦ敞瑙ｆ彁閱掕嚜宸扁€?/strong>鈥嬶紝姣斿@EqualsAndHashCode.Exclude鎺掗櫎闈炲叧閿瓧娈?/li>
- 鈥?strong>鈥嬪畾鏈熺敤SonarLint鎵弿鈥?/strong>鈥嬶紝瀹冭兘鎻嚭90%浠ヤ笂鐨勬柟娉曢噸鍐欓棶棰?/li>
鏈€鍚庣垎涓涓氱寷鏂欙細鐜板湪寰堝鍥㈤槦寮€濮嬬敤鈥?strong>鈥婻ecord绫烩€?/strong>鈥嬶紙Java16+鐗规€э級鏇夸唬甯歌瀹炰綋绫伙紝鑷姩鐢熸垚鍚堢悊鐨別quals/hashCode/toString鏂规硶銆傛瘮濡傦細
java澶嶅埗public record User(String userId, String phone) {}
杩欑帺鎰忕敓鎴愮殑equals鏂规硶鏃㈠畨鍏ㄥ張楂樻晥锛岃涓嶅畾杩囧嚑骞村挶浠氨涓嶇敤鍐嶆墜鍔ㄥ啓杩欎簺鏂规硶浜嗭紒涓嶈繃鍦ㄩ偅涔嬪墠锛岃繕鏄緱鎶婅繖浜涘熀鏈姛缁冩墡瀹炰笉鏄紵