銆銆鏂規硶1錛氶噰鐢?Object#toString()鏂規硶
銆銆璇風湅涓嬮潰鐨勪緥瀛愶細銆銆
銆銆 Object object = getObject();銆銆
銆銆System.out.println(object.toString());銆銆
銆銆鍦ㄨ繖縐嶄嬌鐢ㄦ柟娉曚腑錛屽洜涓簀ava.lang.Object綾婚噷宸叉湁public鏂規硶.toString()錛屾墍浠ュ浠諱綍涓ユ牸鎰忎箟涓婄殑java瀵硅薄閮藉彲浠ヨ皟鐢ㄦ鏂規硶銆備絾鍦ㄤ嬌鐢ㄦ椂瑕佹敞鎰忥紝蹇呴』淇濊瘉object涓嶆槸null鍊鹼紝鍚﹀垯灝嗘姏鍑篘ullPointerException寮傚父銆傞噰鐢ㄨ繖縐嶆柟娉曟椂錛岄氬父媧劇敓綾諱細瑕嗙洊Object閲岀殑toString錛堬級鏂規硶銆傘銆
銆銆鏂規硶2錛氶噰鐢ㄧ被鍨嬭漿鎹紙String錛塷bject鏂規硶
銆銆榪欐槸鏍囧噯鐨勭被鍨嬭漿鎹紝灝唎bject杞垚String綾誨瀷鐨勫箋備嬌鐢ㄨ繖縐嶆柟娉曟椂錛岄渶瑕佹敞鎰忕殑鏄被鍨嬪繀欏昏兘杞垚String綾誨瀷銆傚洜姝ゆ渶濂界敤instanceof鍋氫釜綾誨瀷媯鏌ワ紝浠ュ垽鏂槸鍚﹀彲浠ヨ漿鎹€傚惁鍒欏鏄撴姏鍑篊alssCastException寮傚父銆傛澶栵紝闇鐗瑰埆灝忓績鐨勬槸鍥犲畾涔変負Object 綾誨瀷鐨勫璞″湪杞垚String鏃惰娉曟鏌ュ茍涓嶄細鎶ラ敊錛岃繖灝嗗彲鑳藉鑷存綔鍦ㄧ殑閿欒瀛樺湪銆傝繖鏃惰鏍煎灝忓績銆傚錛氥銆
銆銆Object obj = new Integer(100);銆銆
銆銆String strVal = (String)obj;銆銆
銆銆鍦ㄨ繍琛屾椂灝嗕細鍑洪敊錛屽洜涓哄皢Integer綾誨瀷寮哄埗杞崲涓篠tring綾誨瀷錛屾棤娉曢氳繃銆備絾鏄紝銆銆
銆銆Integer obj = new Integer(100);銆銆
銆銆String strVal = (String)obj;銆銆
銆銆濡傛槸鏍煎紡浠ｇ爜錛屽皢浼氭姤璇硶閿欒銆傘銆
銆銆姝ゅ錛屽洜null鍊煎彲浠ュ己鍒惰漿鎹負浠諱綍java綾葷被鍨嬶紝(String)null涔熸槸鍚堟硶鐨勩傘銆
銆銆鏂規硶3錛氶噰鐢⊿tring.valueOf(Object)
銆銆String.valueOf(Object)鐨勫熀紜鏄疧bject#toString()銆備絾瀹冧笌Object#toString()鍙堟湁鎵涓嶅悓銆傚湪鍓嶉潰鏂規硶1鐨勫垎鏋愪腑鎻愬埌錛屼嬌鐢ㄥ悗鑰呮椂闇淇濊瘉涓嶄負null銆備絾閲囩敤絎笁縐嶆柟娉曟椂錛屽皢涓嶇敤鎷呭績object鏄惁涓簄ull鍊艱繖涓闂銆備負浜嗕究浜庤鏄庨棶棰橈紝鎴戜滑鏉ュ垎鏋愪竴涓嬬浉鍏崇殑婧愪唬鐮併侸dk閲孲tring# valueOf(Object)婧愮爜濡備笅錛氥銆
銆銆 /**
銆銆 * Returns the string representation of the Object argument.
銆銆 *銆銆
銆銆 * @param obj an Object.銆銆
銆銆 * @return if the argument is null, then a string equal to銆銆
銆銆 * "null"; otherwise, the value of銆
銆銆 * obj.toString() is returned.銆銆
銆銆 * @see java.lang.Object#toString()銆銆
銆銆 */銆
銆銆 public static String valueOf(Object obj) {銆銆
銆銆 return (obj == null) ? "null" : obj.toString();銆
銆銆}
銆銆
銆銆浠庝笂闈㈢殑婧愮爜鍙互寰堟竻鏅扮殑鐪嬪嚭null鍊間笉鐢ㄦ媴蹇冪殑鐞嗙敱銆備絾鏄紝榪欎篃鎭版伆緇欎簡鎴戜滑闅愭偅銆傛垜浠簲褰撴敞鎰忓埌錛屽綋object涓簄ull鏃訛紝String.valueOf錛坥bject錛夌殑鍊兼槸瀛楃涓?#8221;null”錛岃屼笉鏄痭ull錛侊紒錛佸湪浣跨敤榪囩▼涓垏璁拌娉ㄦ剰銆傝瘯鎯充竴涓嬶紝濡傛灉鎴戜滑鐢?if(String.valueOf錛坥bject錛?=null){System.out.println(“浼犲叆鐨勫兼槸null錛?#8221;);}榪欐牱鐨勮鍙ュ皢鍙兘浼氬彂鐢熶粈涔堥棶棰樸傚啀鎯充竴涓嬶紝鍚戞帶鍒跺彴杈撳嚭鏃訛紝鍦ㄨ瑙変笂濡備笅璇彞鍦ㄦ墽琛岀殑緇撴灉涓婃湁浠涔堜笉鍚岋細銆銆
銆銆System.out.println(String.valueOf(null));銆銆
銆銆System.out.println(null);銆銆
銆銆鎴戜滑鐪嬪埌鐨勮緭鍑哄皢鏄竴妯′竴鏍風殑涓滆タ錛歯ull錛屼絾瀹冧滑鎰忎箟鐩稿悓鍚楋紵銆銆
銆銆浠ヤ笂鏄object瀵硅薄杞崲涓篠tring鐨勪竴浜涙葷粨銆?
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