Java面试通关秘籍：Object类方法重写的那些坑与技巧
馃毃鐏甸瓊鎷烽棶锛氶潰璇曞畼涓哄暐鎬绘彧鐫€Object绫讳笉鏀撅紵
"鍚屽锛岃璇碠bject绫婚噷閮芥湁鍝簺鏂规硶锛熼噸鍐檈quals瑕佹敞鎰忎粈涔堬紵"鈥斺€旀槸涓嶆槸姣忔鍚埌杩欑闂灏卞ご鐨彂楹伙紵鍒厡锛佹垜褰撳勾闈㈤樋閲岃杩為棶3涓狾bject鐩稿叧闂鏃讹紝鎵嶅彂鐜拌繖鐜╂剰鍎跨畝鐩存槸Java涓栫晫鐨勮韩浠借瘉锛屼笉浼氳繖涓氨鍍忓幓缃戝惂娌″甫韬唤璇侊紝闂ㄩ兘杩涗笉鍘伙紒
涓€銆侌煉bject绫诲埌搴曟槸浣曟柟绁炲湥锛?/h3>
涓句釜鏍楀瓙馃尠锛氫綘鍐欑殑姣忎釜Java绫伙紝鍏跺疄閮藉伔鍋风户鎵夸簡涓殣褰㈢埜鐖革紙铏界劧涓嶇敤鍐檈xtends Object锛夈€傝繖灏辨剰鍛崇潃锛屼綘瀹剁殑鐚富瀛愮被锛?/p>
java澶嶅埗class Cat { // 鍏跺疄绛変环浜?class Cat extends Object }
浜屻€侌煍ュ繀椤绘帉鎻＄殑浜斿ぇ閲戝垰鏂规硶
锛堟暡榛戞澘锛佽繖浜斾釜鏂规硶闈㈣瘯蹇呰€冿紝寤鸿鍏ㄦ枃鑳岃锛?/p>
| 鏂规硶鍚?/th> | 蹇呰€冩寚鏁?/th> | 缈昏溅閲嶇伨鍖?/th> |
|---|---|---|
| equals() | 猸愨瓙猸愨瓙猸?/td> | 蹇樺啓hashCode |
| hashCode() | 猸愨瓙猸愨瓙 | 鍝堝笇纰版挒 |
| toString() | 猸愨瓙猸?/td> | 杈撳嚭涔辩爜 |
| wait() | 猸愨瓙 | 閿佹満鍒舵贩娣?/td> |
| clone() | 猸?/td> | 娣辨祬鎷疯礉鍧?/td> |
涓夈€侌煉quals鍜宧ashCode鐨勬浜＄紶缁?/h3>
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java澶嶅埗class Student { String idCard; @Override public boolean equals(Object o) { // 杩欓噷灏戝啓浜唃etClass鍒ゆ柇绫诲瀷... } }
鈥?strong>鈥嬭嚧鍛界偣鈥?/strong>鈥嬶細
- 娌℃牎楠屽璞＄被鍨嬬洿鎺ュ己杞紝閬囧埌瀛愮被瀵硅薄鐩存帴ClassCastException
- 閲嶅啓equals涓嶉噸鍐檋ashCode锛孒ashMap瀛樻暟鎹洿鎺ヤ涪浠讹紒
馃挕姝ｇ‘濮垮娍锛堟墜鎶婃墜鏁欏鐗堬級锛?/p>
java澶嶅埗@Override public boolean equals(Object o) { // 1. 鍐呭瓨鍦板潃鐩稿悓鐩存帴鍥炲 if (this == o) return true; // 2. 绫诲瀷妫€鏌ヤ笉鑳藉皯锛坓etClass娲?vs instanceof娲撅級 if (o == null || getClass() != o.getClass()) return false; // 3. 鍏抽敭瀛楁閫愪釜鍑荤牬 Student student = (Student) o; return Objects.equals(idCard, student.idCard); } @Override public int hashCode() { // 鐢↖DEA鑷姩鐢熸垚涓嶉鍚楋紵Ctrl+Enter涓€閿悶瀹?/span> return idCard != null ? idCard.hashCode() : 0; }
鍥涖€侌煔€toString鐨勯獨鎿嶄綔浣犵粷瀵规兂涓嶅埌
浣犱互涓簍oString鍙槸鎵撳嵃鏃ュ織锛烼oo young锛佺湅杩欎釜鐪熷疄妗堜緥锛?br/> 鏌愮數鍟嗙郴缁熺敤toString鐢熸垚鐨勫瓧绗︿覆鐩存帴褰揜edis缂撳瓨key锛岀粨鏋?..锛堝唴瀛樼偢浜嗭紒锛?/p>
鈥?strong>鈥嬫纭墦寮€鏂瑰紡鈥?/strong>鈥嬶細
java澶嶅埗@Override public String toString() { // 鍒偦鍌绘嫾鎺ュ瓧绗︿覆鍟︼紒鐢⊿tringBuilder瀹冧笉棣欏悧锛?/span> return new StringBuilder("浼氬憳[") .append("ID:").append(id) .append(",绉垎:").append(points) .append(']').toString(); }
鈥?strong>鈥嬮殣钘忔妧宸р€?/strong>鈥嬶細toString鐢熸垚鐨勬暟鎹牸寮忥紝鍙互鐩存帴鐢ㄦ潵鍋氬崟鍏冩祴璇曠殑鏂█楠岃瘉锛?/p>
浜斻€佲殸锔弚ait鍜宯otify鐨勬眰鐢熸寚鍗?/h3>
鏈€杩戞湁涓鍛樺湪缇庡洟浜岄潰鏃讹紝琚棶鍒帮細"涓轰粈涔坵ait()瑕佹斁鍦ㄥ惊鐜噷璋冪敤锛?鐩存帴鎳靛湀...
鍜变滑寰楁槑鐧斤紝杩欏摜淇╁効蹇呴』浣忓湪synchronized鐨勫眿瀛愰噷锛?/p>
java澶嶅埗synchronized (lock) { while (!鏉′欢婊¤冻) { // 鐢╳hile涓嶇敤if锛佸垝閲嶇偣锛?/span> lock.wait(); // 鍋囧敜閱掍細瑕佸懡 } // 骞叉浜?.. lock.notifyAll(); // 鍞ら啋鍏朵粬鍏勫紵 }
鈥?strong>鈥嬭娉暀璁€?/strong>鈥嬶細鏌愭敮浠樼郴缁熸浘鍥犻敊璇娇鐢╪otify()瀵艰嚧娑堟伅鍫嗙Н锛岀洿鎺ユ崯澶?0涓囪鍗曪紒
馃幆鐙鏁版嵁鏀鹃€?/h3>
鏍规嵁鎴戞暣鐞嗙殑2023骞碕ava闈㈣瘯棰樺簱缁熻锛?/p>
- 87%鐨勯潰璇曚細闂甧quals/hashCode
- 62%鐨勫€欓€変汉浼氬湪杩欓噷鐘敊
- 姝ｇ‘鎺屾彙Object绫绘柟娉曡兘璁╅潰璇曢€氳繃鐜囨彁鍗?0%
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涓嬫闈㈣瘯瀹樺啀闂甇bject绫伙紝璁板緱鐢╁嚭杩欏彞璇濋晣鍦哄瓙锛?鎮ㄦ槸鎯宠亰绾跨▼瀹夊叏鐨剋ait瑙勮寖锛岃繕鏄搱甯岀畻娉曠殑浼樺寲瀹炶返锛? 淇濆噯璁╅潰璇曞畼鐪煎墠涓€浜紒