java 娉涘瀷璇﹁В

Posted 2021-03-16

鏍囩锛?a href='http://www.mamicode.com/so/1/%e6%b7%bb%e5%8a%a0' title='娣诲姞'>娣诲姞   false   size   object   type   and   dom   out   璁块棶   

https://blog.csdn.net/s10461/article/details/53941091

 

 

瀵筳ava鐨勬硾鍨嬬壒鎬х殑浜嗚В浠呴檺浜庤〃闈㈢殑娴呮祬涓€灞傦紝鐩村埌鍦ㄥ涔犺璁℃ā寮忔椂鍙戠幇鏈変笉浜嗚В鐨勭敤娉曪紝鎵嶆兂璧疯缁嗙殑璁板綍涓€涓嬨€?br />鏈枃鍙傝€僯ava 娉涘瀷璇﹁В銆丣ava涓殑娉涘瀷鏂规硶銆?java娉涘瀷璇﹁В
1. 姒傝堪娉涘瀷鍦╦ava涓湁寰堥噸瑕佺殑鍦颁綅锛屽湪闈㈠悜瀵硅薄缂栫▼鍙婂悇绉嶈璁℃ā寮忎腑鏈夐潪甯稿箍娉涚殑搴旂敤銆?br />浠€涔堟槸娉涘瀷锛熶负浠€涔堣浣跨敤娉涘瀷锛?br />娉涘瀷锛屽嵆“鍙傛暟鍖栫被鍨?rdquo;銆備竴鎻愬埌鍙傛暟锛屾渶鐔熸倝鐨勫氨鏄畾涔夋柟娉曟椂鏈夊舰鍙傦紝鐒跺悗璋冪敤姝ゆ柟娉曟椂浼犻€掑疄鍙傘€傞偅涔堝弬鏁板寲绫诲瀷鎬庝箞鐞嗚В鍛紵椤惧悕鎬濅箟锛屽氨鏄皢绫诲瀷鐢卞師鏉ョ殑鍏蜂綋鐨勭被鍨嬪弬鏁板寲锛岀被浼间簬鏂规硶涓殑鍙橀噺鍙傛暟锛屾鏃剁被鍨嬩篃瀹氫箟鎴愬弬鏁板舰寮忥紙鍙互绉颁箣涓虹被鍨嬪舰鍙傦級锛岀劧鍚庡湪浣跨敤/璋冪敤鏃朵紶鍏ュ叿浣撶殑绫诲瀷锛堢被鍨嬪疄鍙傦級銆?br />娉涘瀷鐨勬湰璐ㄦ槸涓轰簡鍙傛暟鍖栫被鍨嬶紙鍦ㄤ笉鍒涘缓鏂扮殑绫诲瀷鐨勬儏鍐典笅锛岄€氳繃娉涘瀷鎸囧畾鐨勪笉鍚岀被鍨嬫潵鎺у埗褰㈠弬鍏蜂綋闄愬埗鐨勭被鍨嬶級銆備篃灏辨槸璇村湪娉涘瀷浣跨敤杩囩▼涓紝鎿嶄綔鐨勬暟鎹被鍨嬭鎸囧畾涓轰竴涓弬鏁帮紝杩欑鍙傛暟绫诲瀷鍙互鐢ㄥ湪绫汇€佹帴鍙ｅ拰鏂规硶涓紝鍒嗗埆琚О涓烘硾鍨嬬被銆佹硾鍨嬫帴鍙ｃ€佹硾鍨嬫柟娉曘€?br />2. 涓€涓牀瀛愪竴涓涓句簡鏃犳暟娆＄殑渚嬪瓙锛?br />List arrayList = new ArrayList();arrayList.add("aaaa");arrayList.add(100);
for(int i = 0; i< arrayList.size();i++){    String item = (String)arrayList.get(i);    Log.d("娉涘瀷娴嬭瘯","item = " + item);}12345678姣棤鐤戦棶锛岀▼搴忕殑杩愯缁撴灉浼氫互宕╂簝缁撴潫锛?br />java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String1ArrayList鍙互瀛樻斁浠绘剰绫诲瀷锛屼緥瀛愪腑娣诲姞浜嗕竴涓猄tring绫诲瀷锛屾坊鍔犱簡涓€涓狪nteger绫诲瀷锛屽啀浣跨敤鏃堕兘浠tring鐨勬柟寮忎娇鐢紝鍥犳绋嬪簭宕╂簝浜嗐€備负浜嗚В鍐崇被浼艰繖鏍风殑闂锛堝湪缂栬瘧闃舵灏卞彲浠ヨВ鍐筹級锛屾硾鍨嬪簲杩愯€岀敓銆?br />鎴戜滑灏嗙涓€琛屽０鏄庡垵濮嬪寲list鐨勪唬鐮佹洿鏀逛竴涓嬶紝缂栬瘧鍣ㄤ細鍦ㄧ紪璇戦樁娈靛氨鑳藉甯垜浠彂鐜扮被浼艰繖鏍风殑闂銆?br />List<String> arrayList = new ArrayList<String>();...//arrayList.add(100); 鍦ㄧ紪璇戦樁娈碉紝缂栬瘧鍣ㄥ氨浼氭姤閿?233. 鐗规€ф硾鍨嬪彧鍦ㄧ紪璇戦樁娈垫湁鏁堛€傜湅涓嬮潰鐨勪唬鐮侊細
List<String> stringArrayList = new ArrayList<String>();List<Integer> integerArrayList = new ArrayList<Integer>();
Class classStringArrayList = stringArrayList.getClass();Class classIntegerArrayList = integerArrayList.getClass();
if(classStringArrayList.equals(classIntegerArrayList)){    Log.d("娉涘瀷娴嬭瘯","绫诲瀷鐩稿悓");}123456789杈撳嚭缁撴灉锛欴/娉涘瀷娴嬭瘯: 绫诲瀷鐩稿悓銆?br />閫氳繃涓婇潰鐨勪緥瀛愬彲浠ヨ瘉鏄庯紝鍦ㄧ紪璇戜箣鍚庣▼搴忎細閲囧彇鍘绘硾鍨嬪寲鐨勬帾鏂姐€備篃灏辨槸璇碕ava涓殑娉涘瀷锛屽彧鍦ㄧ紪璇戦樁娈垫湁鏁堛€傚湪缂栬瘧杩囩▼涓紝姝ｇ‘妫€楠屾硾鍨嬬粨鏋滃悗锛屼細灏嗘硾鍨嬬殑鐩稿叧淇℃伅鎿﹀嚭锛屽苟涓斿湪瀵硅薄杩涘叆鍜岀寮€鏂规硶鐨勮竟鐣屽娣诲姞绫诲瀷妫€鏌ュ拰绫诲瀷杞崲鐨勬柟娉曘€備篃灏辨槸璇达紝娉涘瀷淇℃伅涓嶄細杩涘叆鍒拌繍琛屾椂闃舵銆?br />瀵规鎬荤粨鎴愪竴鍙ヨ瘽锛氭硾鍨嬬被鍨嬪湪閫昏緫涓婄湅浠ョ湅鎴愭槸澶氫釜涓嶅悓鐨勭被鍨嬶紝瀹為檯涓婇兘鏄浉鍚岀殑鍩烘湰绫诲瀷銆?br />4. 娉涘瀷鐨勪娇鐢ㄦ硾鍨嬫湁涓夌浣跨敤鏂瑰紡锛屽垎鍒负锛氭硾鍨嬬被銆佹硾鍨嬫帴鍙ｃ€佹硾鍨嬫柟娉?br />4.3 娉涘瀷绫绘硾鍨嬬被鍨嬬敤浜庣被鐨勫畾涔変腑锛岃绉颁负娉涘瀷绫汇€傞€氳繃娉涘瀷鍙互瀹屾垚瀵逛竴缁勭被鐨勬搷浣滃澶栧紑鏀剧浉鍚岀殑鎺ュ彛銆傛渶鍏稿瀷鐨勫氨鏄悇绉嶅鍣ㄧ被锛屽锛歀ist銆丼et銆丮ap銆?br />娉涘瀷绫荤殑鏈€鍩烘湰鍐欐硶锛堣繖涔堢湅鍙兘浼氭湁鐐规檿锛屼細鍦ㄤ笅闈㈢殑渚嬪瓙涓瑙ｏ級锛?br />class 绫诲悕绉?<娉涘瀷鏍囪瘑锛氬彲浠ラ殢渚垮啓浠绘剰鏍囪瘑鍙凤紝鏍囪瘑鎸囧畾鐨勬硾鍨嬬殑绫诲瀷>{  private 娉涘瀷鏍囪瘑 /*锛堟垚鍛樺彉閲忕被鍨嬶級*/ var;   .....
  }}123456涓€涓渶鏅€氱殑娉涘瀷绫伙細
//姝ゅT鍙互闅忎究鍐欎负浠绘剰鏍囪瘑锛屽父瑙佺殑濡俆銆丒銆並銆乂绛夊舰寮忕殑鍙傛暟甯哥敤浜庤〃绀烘硾鍨?/鍦ㄥ疄渚嬪寲娉涘瀷绫绘椂锛屽繀椤绘寚瀹歍鐨勫叿浣撶被鍨媝ublic class Generic<T>{     //key杩欎釜鎴愬憳鍙橀噺鐨勭被鍨嬩负T,T鐨勭被鍨嬬敱澶栭儴鎸囧畾      private T key;
    public Generic(T key) { //娉涘瀷鏋勯€犳柟娉曞舰鍙俴ey鐨勭被鍨嬩篃涓篢锛孴鐨勭被鍨嬬敱澶栭儴鎸囧畾        this.key = key;    }
    public T getKey(){ //娉涘瀷鏂规硶getKey鐨勮繑鍥炲€肩被鍨嬩负T锛孴鐨勭被鍨嬬敱澶栭儴鎸囧畾        return key;    }}1234567891011121314//娉涘瀷鐨勭被鍨嬪弬鏁板彧鑳芥槸绫荤被鍨嬶紙鍖呮嫭鑷畾涔夌被锛夛紝涓嶈兘鏄畝鍗曠被鍨?/浼犲叆鐨勫疄鍙傜被鍨嬮渶涓庢硾鍨嬬殑绫诲瀷鍙傛暟绫诲瀷鐩稿悓锛屽嵆涓篒nteger.Generic<Integer> genericInteger = new Generic<Integer>(123456);
//浼犲叆鐨勫疄鍙傜被鍨嬮渶涓庢硾鍨嬬殑绫诲瀷鍙傛暟绫诲瀷鐩稿悓锛屽嵆涓篠tring.Generic<String> genericString = new Generic<String>("key_vlaue");Log.d("娉涘瀷娴嬭瘯","key is " + genericInteger.getKey());Log.d("娉涘瀷娴嬭瘯","key is " + genericString.getKey());1234567812-27 09:20:04.432 13063-13063/? D/娉涘瀷娴嬭瘯: key is 12345612-27 09:20:04.432 13063-13063/? D/娉涘瀷娴嬭瘯: key is key_vlaue12瀹氫箟鐨勬硾鍨嬬被锛屽氨涓€瀹氳浼犲叆娉涘瀷绫诲瀷瀹炲弬涔堬紵骞朵笉鏄繖鏍凤紝鍦ㄤ娇鐢ㄦ硾鍨嬬殑鏃跺€欏鏋滀紶鍏ユ硾鍨嬪疄鍙傦紝鍒欎細鏍规嵁浼犲叆鐨勬硾鍨嬪疄鍙傚仛鐩稿簲鐨勯檺鍒讹紝姝ゆ椂娉涘瀷鎵嶄細璧峰埌鏈簲璧峰埌鐨勯檺鍒朵綔鐢ㄣ€傚鏋滀笉浼犲叆娉涘瀷绫诲瀷瀹炲弬鐨勮瘽锛屽湪娉涘瀷绫讳腑浣跨敤娉涘瀷鐨勬柟娉曟垨鎴愬憳鍙橀噺瀹氫箟鐨勭被鍨嬪彲浠ヤ负浠讳綍鐨勭被鍨嬨€?br />鐪嬩竴涓緥瀛愶細
Generic generic = new Generic("111111");Generic generic1 = new Generic(4444);Generic generic2 = new Generic(55.55);Generic generic3 = new Generic(false);
Log.d("娉涘瀷娴嬭瘯","key is " + generic.getKey());Log.d("娉涘瀷娴嬭瘯","key is " + generic1.getKey());Log.d("娉涘瀷娴嬭瘯","key is " + generic2.getKey());Log.d("娉涘瀷娴嬭瘯","key is " + generic3.getKey());123456789D/娉涘瀷娴嬭瘯: key is 111111D/娉涘瀷娴嬭瘯: key is 4444D/娉涘瀷娴嬭瘯: key is 55.55D/娉涘瀷娴嬭瘯: key is false1234娉ㄦ剰锛?br />娉涘瀷鐨勭被鍨嬪弬鏁板彧鑳芥槸绫荤被鍨嬶紝涓嶈兘鏄畝鍗曠被鍨嬨€備笉鑳藉纭垏鐨勬硾鍨嬬被鍨嬩娇鐢╥nstanceof鎿嶄綔銆傚涓嬮潰鐨勬搷浣滄槸闈炴硶鐨勶紝缂栬瘧鏃朵細鍑洪敊銆?br />if(ex_num instanceof Generic<Number>){   } 124.4 娉涘瀷鎺ュ彛娉涘瀷鎺ュ彛涓庢硾鍨嬬被鐨勫畾涔夊強浣跨敤鍩烘湰鐩稿悓銆傛硾鍨嬫帴鍙ｅ父琚敤鍦ㄥ悇绉嶇被鐨勭敓浜у櫒涓紝鍙互鐪嬩竴涓緥瀛愶細
//瀹氫箟涓€涓硾鍨嬫帴鍙ublic interface Generator<T> {    public T next();}1234褰撳疄鐜版硾鍨嬫帴鍙ｇ殑绫伙紝鏈紶鍏ユ硾鍨嬪疄鍙傛椂锛?br />/** * 鏈紶鍏ユ硾鍨嬪疄鍙傛椂锛屼笌娉涘瀷绫荤殑瀹氫箟鐩稿悓锛屽湪澹版槑绫荤殑鏃跺€欙紝闇€灏嗘硾鍨嬬殑澹版槑涔熶竴璧峰姞鍒扮被涓?nbsp;* 鍗筹細class FruitGenerator<T> implements Generator<T>{ * 濡傛灉涓嶅０鏄庢硾鍨嬶紝濡傦細class FruitGenerator implements Generator<T>锛岀紪璇戝櫒浼氭姤閿欙細"Unknown class" */class FruitGenerator<T> implements Generator<T>{    @Override    public T next() {        return null;    }}1234567891011褰撳疄鐜版硾鍨嬫帴鍙ｇ殑绫伙紝浼犲叆娉涘瀷瀹炲弬鏃讹細
/** * 浼犲叆娉涘瀷瀹炲弬鏃讹細 * 瀹氫箟涓€涓敓浜у櫒瀹炵幇杩欎釜鎺ュ彛,铏界劧鎴戜滑鍙垱寤轰簡涓€涓硾鍨嬫帴鍙enerator<T> * 浣嗘槸鎴戜滑鍙互涓篢浼犲叆鏃犳暟涓疄鍙傦紝褰㈡垚鏃犳暟绉嶇被鍨嬬殑Generator鎺ュ彛銆?nbsp;* 鍦ㄥ疄鐜扮被瀹炵幇娉涘瀷鎺ュ彛鏃讹紝濡傚凡灏嗘硾鍨嬬被鍨嬩紶鍏ュ疄鍙傜被鍨嬶紝鍒欐墍鏈変娇鐢ㄦ硾鍨嬬殑鍦版柟閮借鏇挎崲鎴愪紶鍏ョ殑瀹炲弬绫诲瀷 * 鍗筹細Generator<T>锛宲ublic T next();涓殑鐨凾閮借鏇挎崲鎴愪紶鍏ョ殑String绫诲瀷銆?nbsp;*/public class FruitGenerator implements Generator<String> {
    private String[] fruits = new String[]{"Apple", "Banana", "Pear"};
    @Override    public String next() {        Random rand = new Random();        return fruits[rand.nextInt(3)];    }}12345678910111213141516174.5 娉涘瀷閫氶厤绗︽垜浠煡閬揑ngeter鏄疦umber鐨勪竴涓瓙绫伙紝鍚屾椂鍦ㄧ壒鎬х珷鑺備腑鎴戜滑涔熼獙璇佽繃Generic<Ingeter>涓嶨eneric<Number>瀹為檯涓婃槸鐩稿悓鐨勪竴绉嶅熀鏈被鍨嬨€傞偅涔堥棶棰樻潵浜嗭紝鍦ㄤ娇鐢℅eneric<Number>浣滀负褰㈠弬鐨勬柟娉曚腑锛岃兘鍚︿娇鐢℅eneric<Ingeter>鐨勫疄渚嬩紶鍏ュ憿锛熷湪閫昏緫涓婄被浼间簬Generic<Number>鍜孏eneric<Ingeter>鏄惁鍙互鐪嬫垚鍏锋湁鐖跺瓙鍏崇郴鐨勬硾鍨嬬被鍨嬪憿锛?br />涓轰簡寮勬竻妤氳繖涓棶棰橈紝鎴戜滑浣跨敤Generic<T>杩欎釜娉涘瀷绫荤户缁湅涓嬮潰鐨勪緥瀛愶細
public void showKeyValue1(Generic<Number> obj){    Log.d("娉涘瀷娴嬭瘯","key value is " + obj.getKey());}123Generic<Integer> gInteger = new Generic<Integer>(123);Generic<Number> gNumber = new Generic<Number>(456);
showKeyValue(gNumber);
// showKeyValue杩欎釜鏂规硶缂栬瘧鍣ㄤ細涓烘垜浠姤閿欙細Generic<java.lang.Integer> // cannot be applied to Generic<java.lang.Number>// showKeyValue(gInteger);12345678閫氳繃鎻愮ず淇℃伅鎴戜滑鍙互鐪嬪埌Generic<Integer>涓嶈兘琚湅浣滀负`Generic<Number>鐨勫瓙绫汇€傜敱姝ゅ彲浠ョ湅鍑?鍚屼竴绉嶆硾鍨嬪彲浠ュ搴斿涓増鏈紙鍥犱负鍙傛暟绫诲瀷鏄笉纭畾鐨勶級锛屼笉鍚岀増鏈殑娉涘瀷绫诲疄渚嬫槸涓嶅吋瀹圭殑銆?br />鍥炲埌涓婇潰鐨勪緥瀛愶紝濡備綍瑙ｅ喅涓婇潰鐨勯棶棰橈紵鎬讳笉鑳戒负浜嗗畾涔変竴涓柊鐨勬柟娉曟潵澶勭悊Generic<Integer>绫诲瀷鐨勭被锛岃繖鏄剧劧涓巎ava涓殑澶氬彴鐞嗗康鐩歌繚鑳屻€傚洜姝ゆ垜浠渶瑕佷竴涓湪閫昏緫涓婂彲浠ヨ〃绀哄悓鏃舵槸Generic<Integer>鍜孏eneric<Number>鐖剁被鐨勫紩鐢ㄧ被鍨嬨€傜敱姝ょ被鍨嬮€氶厤绗﹀簲杩愯€岀敓銆?br />鎴戜滑鍙互灏嗕笂闈㈢殑鏂规硶鏀逛竴涓嬶細
public void showKeyValue1(Generic<?> obj){    Log.d("娉涘瀷娴嬭瘯","key value is " + obj.getKey());}123绫诲瀷閫氶厤绗︿竴鑸槸浣跨敤锛熶唬鏇垮叿浣撶殑绫诲瀷瀹炲弬锛屾敞鎰忎簡锛屾澶?rsquo;锛?rsquo;鏄被鍨嬪疄鍙傦紝鑰屼笉鏄被鍨嬪舰鍙?銆傞噸瑕佽涓夐亶锛佹澶?rsquo;锛?rsquo;鏄被鍨嬪疄鍙傦紝鑰屼笉鏄被鍨嬪舰鍙?锛?姝ゅ’锛?rsquo;鏄被鍨嬪疄鍙傦紝鑰屼笉鏄被鍨嬪舰鍙?锛佸啀鐩寸櫧鐐圭殑鎰忔€濆氨鏄紝姝ゅ鐨勶紵鍜孨umber銆丼tring銆両nteger涓€鏍烽兘鏄竴绉嶅疄闄呯殑绫诲瀷锛屽彲浠ユ妸锛熺湅鎴愭墍鏈夌被鍨嬬殑鐖剁被銆傛槸涓€绉嶇湡瀹炵殑绫诲瀷銆?br />鍙互瑙ｅ喅褰撳叿浣撶被鍨嬩笉纭畾鐨勬椂鍊欙紝杩欎釜閫氶厤绗﹀氨鏄??  锛涘綋鎿嶄綔绫诲瀷鏃讹紝涓嶉渶瑕佷娇鐢ㄧ被鍨嬬殑鍏蜂綋鍔熻兘鏃讹紝鍙娇鐢∣bject绫讳腑鐨勫姛鑳姐€傞偅涔堝彲浠ョ敤 ? 閫氶厤绗︽潵琛ㄦ湭鐭ョ被鍨嬨€?br />4.6 娉涘瀷鏂规硶鍦╦ava涓?娉涘瀷绫荤殑瀹氫箟闈炲父绠€鍗曪紝浣嗘槸娉涘瀷鏂规硶灏辨瘮杈冨鏉備簡銆?br />灏ゅ叾鏄垜浠鍒扮殑澶у鏁版硾鍨嬬被涓殑鎴愬憳鏂规硶涔熼兘浣跨敤浜嗘硾鍨嬶紝鏈夌殑鐢氳嚦娉涘瀷绫讳腑涔熷寘鍚潃娉涘瀷鏂规硶锛岃繖鏍峰湪鍒濆鑰呬腑闈炲父瀹规槗灏嗘硾鍨嬫柟娉曠悊瑙ｉ敊浜嗐€?br />娉涘瀷绫伙紝鏄湪瀹炰緥鍖栫被鐨勬椂鍊欐寚鏄庢硾鍨嬬殑鍏蜂綋绫诲瀷锛涙硾鍨嬫柟娉曪紝鏄湪璋冪敤鏂规硶鐨勬椂鍊欐寚鏄庢硾鍨嬬殑鍏蜂綋绫诲瀷 銆?br />/** * 娉涘瀷鏂规硶鐨勫熀鏈粙缁?nbsp;* @param tClass 浼犲叆鐨勬硾鍨嬪疄鍙?nbsp;* @return T 杩斿洖鍊间负T绫诲瀷 * 璇存槑锛?nbsp;*     1锛塸ublic 涓?杩斿洖鍊间腑闂?lt;T>闈炲父閲嶈锛屽彲浠ョ悊瑙ｄ负澹版槑姝ゆ柟娉曚负娉涘瀷鏂规硶銆?nbsp;*     2锛夊彧鏈夊０鏄庝簡<T>鐨勬柟娉曟墠鏄硾鍨嬫柟娉曪紝娉涘瀷绫讳腑鐨勪娇鐢ㄤ簡娉涘瀷鐨勬垚鍛樻柟娉曞苟涓嶆槸娉涘瀷鏂规硶銆?nbsp;*     3锛?lt;T>琛ㄦ槑璇ユ柟娉曞皢浣跨敤娉涘瀷绫诲瀷T锛屾鏃舵墠鍙互鍦ㄦ柟娉曚腑浣跨敤娉涘瀷绫诲瀷T銆?nbsp;*     4锛変笌娉涘瀷绫荤殑瀹氫箟涓€鏍凤紝姝ゅT鍙互闅忎究鍐欎负浠绘剰鏍囪瘑锛屽父瑙佺殑濡俆銆丒銆並銆乂绛夊舰寮忕殑鍙傛暟甯哥敤浜庤〃绀烘硾鍨嬨€?nbsp;*/public <T> T genericMethod(Class<T> tClass)throws InstantiationException ,  IllegalAccessException{        T instance = tClass.newInstance();        return instance;}123456789101112131415Object obj = genericMethod(Class.forName("com.test.test"));14.6.1 娉涘瀷鏂规硶鐨勫熀鏈敤娉曞厜鐪嬩笂闈㈢殑渚嬪瓙鏈夌殑鍚屽鍙兘渚濈劧浼氶潪甯歌糠绯婏紝鎴戜滑鍐嶉€氳繃涓€涓緥瀛愶紝鎶婃垜娉涘瀷鏂规硶鍐嶆€荤粨涓€涓嬨€?br />public class GenericTest {   //杩欎釜绫绘槸涓硾鍨嬬被锛屽湪涓婇潰宸茬粡浠嬬粛杩?nbsp;  public class Generic<T>{             private T key;
        public Generic(T key) {            this.key = key;        }
        //鎴戞兂璇寸殑鍏跺疄鏄繖涓紝铏界劧鍦ㄦ柟娉曚腑浣跨敤浜嗘硾鍨嬶紝浣嗘槸杩欏苟涓嶆槸涓€涓硾鍨嬫柟娉曘€?nbsp;       //杩欏彧鏄被涓竴涓櫘閫氱殑鎴愬憳鏂规硶锛屽彧涓嶈繃浠栫殑杩斿洖鍊兼槸鍦ㄥ０鏄庢硾鍨嬬被宸茬粡澹版槑杩囩殑娉涘瀷銆?nbsp;       //鎵€浠ュ湪杩欎釜鏂规硶涓墠鍙互缁х画浣跨敤 T 杩欎釜娉涘瀷銆?nbsp;       public T getKey(){            return key;        }
        /**         * 杩欎釜鏂规硶鏄剧劧鏄湁闂鐨勶紝鍦ㄧ紪璇戝櫒浼氱粰鎴戜滑鎻愮ず杩欐牱鐨勯敊璇俊鎭?cannot reslove symbol E"         * 鍥犱负鍦ㄧ被鐨勫０鏄庝腑骞舵湭澹版槑娉涘瀷E锛屾墍浠ュ湪浣跨敤E鍋氬舰鍙傚拰杩斿洖鍊肩被鍨嬫椂锛岀紪璇戝櫒浼氭棤娉曡瘑鍒€?nbsp;       public E setKey(E key){             this.key = keu        }        */    }
    /**      * 杩欐墠鏄竴涓湡姝ｇ殑娉涘瀷鏂规硶銆?nbsp;    * 棣栧厛鍦╬ublic涓庤繑鍥炲€间箣闂寸殑<T>蹇呬笉鍙皯锛岃繖琛ㄦ槑杩欐槸涓€涓硾鍨嬫柟娉曪紝骞朵笖澹版槑浜嗕竴涓硾鍨婽     * 杩欎釜T鍙互鍑虹幇鍦ㄨ繖涓硾鍨嬫柟娉曠殑浠绘剰浣嶇疆.     * 娉涘瀷鐨勬暟閲忎篃鍙互涓轰换鎰忓涓?nbsp;     *    濡傦細public <T,K> K showKeyName(Generic<T> container){     *        ...     *        }     */    public <T> T showKeyName(Generic<T> container){        System.out.println("container key :" + container.getKey());        //褰撶劧杩欎釜渚嬪瓙涓剧殑涓嶅お鍚堥€傦紝鍙槸涓轰簡璇存槑娉涘瀷鏂规硶鐨勭壒鎬с€?nbsp;       T test = container.getKey();        return test;    }
    //杩欎篃涓嶆槸涓€涓硾鍨嬫柟娉曪紝杩欏氨鏄竴涓櫘閫氱殑鏂规硶锛屽彧鏄娇鐢ㄤ簡Generic<Number>杩欎釜娉涘瀷绫诲仛褰㈠弬鑰屽凡銆?nbsp;   public void showKeyValue1(Generic<Number> obj){        Log.d("娉涘瀷娴嬭瘯","key value is " + obj.getKey());    }
    //杩欎篃涓嶆槸涓€涓硾鍨嬫柟娉曪紝杩欎篃鏄竴涓櫘閫氱殑鏂规硶锛屽彧涓嶈繃浣跨敤浜嗘硾鍨嬮€氶厤绗?    //鍚屾椂杩欎篃鍗拌瘉浜嗘硾鍨嬮€氶厤绗︾珷鑺傛墍鎻忚堪鐨勶紝?鏄竴绉嶇被鍨嬪疄鍙傦紝鍙互鐪嬪仛涓篘umber绛夋墍鏈夌被鐨勭埗绫?nbsp;   public void showKeyValue2(Generic<?> obj){        Log.d("娉涘瀷娴嬭瘯","key value is " + obj.getKey());    }
     /**     * 杩欎釜鏂规硶鏄湁闂鐨勶紝缂栬瘧鍣ㄤ細涓烘垜浠彁绀洪敊璇俊鎭細"UnKnown class 鈥楨鈥?"     * 铏界劧鎴戜滑澹版槑浜?lt;T>,涔熻〃鏄庝簡杩欐槸涓€涓彲浠ュ鐞嗘硾鍨嬬殑绫诲瀷鐨勬硾鍨嬫柟娉曘€?nbsp;    * 浣嗘槸鍙０鏄庝簡娉涘瀷绫诲瀷T锛屽苟鏈０鏄庢硾鍨嬬被鍨婨锛屽洜姝ょ紪璇戝櫒骞朵笉鐭ラ亾璇ュ浣曞鐞咵杩欎釜绫诲瀷銆?nbsp;   public <T> T showKeyName(Generic<E> container){        ...    }      */
    /**     * 杩欎釜鏂规硶涔熸槸鏈夐棶棰樼殑锛岀紪璇戝櫒浼氫负鎴戜滑鎻愮ず閿欒淇℃伅锛?UnKnown class 鈥楾鈥?"     * 瀵逛簬缂栬瘧鍣ㄦ潵璇碩杩欎釜绫诲瀷骞舵湭椤圭洰涓０鏄庤繃锛屽洜姝ょ紪璇戜篃涓嶇煡閬撹濡備綍缂栬瘧杩欎釜绫汇€?nbsp;    * 鎵€浠ヨ繖涔熶笉鏄竴涓纭殑娉涘瀷鏂规硶澹版槑銆?nbsp;   public void showkey(T genericObj){
    }    */
    public static void main(String[] args) {

    }}1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374754.6.2 绫讳腑鐨勬硾鍨嬫柟娉曞綋鐒惰繖骞朵笉鏄硾鍨嬫柟娉曠殑鍏ㄩ儴锛屾硾鍨嬫柟娉曞彲浠ュ嚭鐜版潅浠讳綍鍦版柟鍜屼换浣曞満鏅腑浣跨敤銆備絾鏄湁涓€绉嶆儏鍐垫槸闈炲父鐗规畩鐨勶紝褰撴硾鍨嬫柟娉曞嚭鐜板湪娉涘瀷绫讳腑鏃讹紝鎴戜滑鍐嶉€氳繃涓€涓緥瀛愮湅涓€涓?br />public class GenericFruit {    class Fruit{        @Override        public String toString() {            return "fruit";        }    }
    class Apple extends Fruit{        @Override        public String toString() {            return "apple";        }    }
    class Person{        @Override        public String toString() {            return "Person";        }    }
    class GenerateTest<T>{        public void show_1(T t){            System.out.println(t.toString());        }
        //鍦ㄦ硾鍨嬬被涓０鏄庝簡涓€涓硾鍨嬫柟娉曪紝浣跨敤娉涘瀷E锛岃繖绉嶆硾鍨婨鍙互涓轰换鎰忕被鍨嬨€傚彲浠ョ被鍨嬩笌T鐩稿悓锛屼篃鍙互涓嶅悓銆?nbsp;       //鐢变簬娉涘瀷鏂规硶鍦ㄥ０鏄庣殑鏃跺€欎細澹版槑娉涘瀷<E>锛屽洜姝ゅ嵆浣垮湪娉涘瀷绫讳腑骞舵湭澹版槑娉涘瀷锛岀紪璇戝櫒涔熻兘澶熸纭瘑鍒硾鍨嬫柟娉曚腑璇嗗埆鐨勬硾鍨嬨€?nbsp;       public <E> void show_3(E t){            System.out.println(t.toString());        }
        //鍦ㄦ硾鍨嬬被涓０鏄庝簡涓€涓硾鍨嬫柟娉曪紝浣跨敤娉涘瀷T锛屾敞鎰忚繖涓猅鏄竴绉嶅叏鏂扮殑绫诲瀷锛屽彲浠ヤ笌娉涘瀷绫讳腑澹版槑鐨凾涓嶆槸鍚屼竴绉嶇被鍨嬨€?nbsp;       public <T> void show_2(T t){            System.out.println(t.toString());        }    }
    public static void main(String[] args) {        Apple apple = new Apple();        Person person = new Person();
        GenerateTest<Fruit> generateTest = new GenerateTest<Fruit>();        //apple鏄疐ruit鐨勫瓙绫伙紝鎵€浠ヨ繖閲屽彲浠?nbsp;       generateTest.show_1(apple);        //缂栬瘧鍣ㄤ細鎶ラ敊锛屽洜涓烘硾鍨嬬被鍨嬪疄鍙傛寚瀹氱殑鏄疐ruit锛岃€屼紶鍏ョ殑瀹炲弬绫绘槸Person        //generateTest.show_1(person);
        //浣跨敤杩欎袱涓柟娉曢兘鍙互鎴愬姛        generateTest.show_2(apple);        generateTest.show_2(person);
        //浣跨敤杩欎袱涓柟娉曚篃閮藉彲浠ユ垚鍔?nbsp;       generateTest.show_3(apple);        generateTest.show_3(person);    }}123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657584.6.3 娉涘瀷鏂规硶涓庡彲鍙樺弬鏁板啀鐪嬩竴涓硾鍨嬫柟娉曞拰鍙彉鍙傛暟鐨勪緥瀛愶細
public <T> void printMsg( T... args){    for(T t : args){        Log.d("娉涘瀷娴嬭瘯","t is " + t);    }}12345printMsg("111",222,"aaaa","2323.4",55.55);14.6.4 闈欐€佹柟娉曚笌娉涘瀷闈欐€佹柟娉曟湁涓€绉嶆儏鍐甸渶瑕佹敞鎰忎竴涓嬶紝閭ｅ氨鏄湪绫讳腑鐨勯潤鎬佹柟娉曚娇鐢ㄦ硾鍨嬶細闈欐€佹柟娉曟棤娉曡闂被涓婂畾涔夌殑娉涘瀷锛涘鏋滈潤鎬佹柟娉曟搷浣滅殑寮曠敤鏁版嵁绫诲瀷涓嶇‘瀹氱殑鏃跺€欙紝蹇呴』瑕佸皢娉涘瀷瀹氫箟鍦ㄦ柟娉曚笂銆?br />鍗筹細濡傛灉闈欐€佹柟娉曡浣跨敤娉涘瀷鐨勮瘽锛屽繀椤诲皢闈欐€佹柟娉曚篃瀹氫箟鎴愭硾鍨嬫柟娉?銆?br />public class StaticGenerator<T> {    ....    ....    /**     * 濡傛灉鍦ㄧ被涓畾涔変娇鐢ㄦ硾鍨嬬殑闈欐€佹柟娉曪紝闇€瑕佹坊鍔犻澶栫殑娉涘瀷澹版槑锛堝皢杩欎釜鏂规硶瀹氫箟鎴愭硾鍨嬫柟娉曪級     * 鍗充娇闈欐€佹柟娉曡浣跨敤娉涘瀷绫讳腑宸茬粡澹版槑杩囩殑娉涘瀷涔熶笉鍙互銆?nbsp;    * 濡傦細public static void show(T t){..},姝ゆ椂缂栬瘧鍣ㄤ細鎻愮ず閿欒淇℃伅锛?nbsp;         "StaticGenerator cannot be refrenced from static context"     */    public static <T> void show(T t){
    }}123456789101112134.6.5 娉涘瀷鏂规硶鎬荤粨娉涘瀷鏂规硶鑳戒娇鏂规硶鐙珛浜庣被鑰屼骇鐢熷彉鍖栵紝浠ヤ笅鏄竴涓熀鏈殑鎸囧鍘熷垯锛?br />鏃犺浣曟椂锛屽鏋滀綘鑳藉仛鍒帮紝浣犲氨璇ュ敖閲忎娇鐢ㄦ硾鍨嬫柟娉曘€備篃灏辨槸璇达紝濡傛灉浣跨敤娉涘瀷鏂规硶灏嗘暣涓被娉涘瀷鍖栵紝閭ｄ箞灏卞簲璇ヤ娇鐢ㄦ硾鍨嬫柟娉曘€傚彟澶栧浜庝竴涓猻tatic鐨勬柟娉曡€屽凡锛屾棤娉曡闂硾鍨嬬被鍨嬬殑鍙傛暟銆傛墍浠ュ鏋渟tatic鏂规硶瑕佷娇鐢ㄦ硾鍨嬭兘鍔涳紝灏卞繀椤讳娇鍏舵垚涓烘硾鍨嬫柟娉曘€?br />4.6 娉涘瀷涓婁笅杈圭晫鍦ㄤ娇鐢ㄦ硾鍨嬬殑鏃跺€欙紝鎴戜滑杩樺彲浠ヤ负浼犲叆鐨勬硾鍨嬬被鍨嬪疄鍙傝繘琛屼笂涓嬭竟鐣岀殑闄愬埗锛屽锛氱被鍨嬪疄鍙傚彧鍑嗕紶鍏ユ煇绉嶇被鍨嬬殑鐖剁被鎴栨煇绉嶇被鍨嬬殑瀛愮被銆?br />涓烘硾鍨嬫坊鍔犱笂杈圭晫锛屽嵆浼犲叆鐨勭被鍨嬪疄鍙傚繀椤绘槸鎸囧畾绫诲瀷鐨勫瓙绫诲瀷
public void showKeyValue1(Generic<? extends Number> obj){    Log.d("娉涘瀷娴嬭瘯","key value is " + obj.getKey());}123Generic<String> generic1 = new Generic<String>("11111");Generic<Integer> generic2 = new Generic<Integer>(2222);Generic<Float> generic3 = new Generic<Float>(2.4f);Generic<Double> generic4 = new Generic<Double>(2.56);
//杩欎竴琛屼唬鐮佺紪璇戝櫒浼氭彁绀洪敊璇紝鍥犱负String绫诲瀷骞朵笉鏄疦umber绫诲瀷鐨勫瓙绫?/showKeyValue1(generic1);
showKeyValue1(generic2);showKeyValue1(generic3);showKeyValue1(generic4);1234567891011濡傛灉鎴戜滑鎶婃硾鍨嬬被鐨勫畾涔変篃鏀逛竴涓?
public class Generic<T extends Number>{    private T key;
    public Generic(T key) {        this.key = key;    }
    public T getKey(){        return key;    }}1234567891011//杩欎竴琛屼唬鐮佷篃浼氭姤閿欙紝鍥犱负String涓嶆槸Number鐨勫瓙绫籊eneric<String> generic1 = new Generic<String>("11111");12鍐嶆潵涓€涓硾鍨嬫柟娉曠殑渚嬪瓙锛?br />//鍦ㄦ硾鍨嬫柟娉曚腑娣诲姞涓婁笅杈圭晫闄愬埗鐨勬椂鍊欙紝蹇呴』鍦ㄦ潈闄愬０鏄庝笌杩斿洖鍊间箣闂寸殑<T>涓婃坊鍔犱笂涓嬭竟鐣岋紝鍗冲湪娉涘瀷澹版槑鐨勬椂鍊欐坊鍔?/public <T> T showKeyName(Generic<T extends Number> container)锛岀紪璇戝櫒浼氭姤閿欙細"Unexpected bound"public <T extends Number> T showKeyName(Generic<T> container){    System.out.println("container key :" + container.getKey());    T test = container.getKey();    return test;}1234567閫氳繃涓婇潰鐨勪袱涓緥瀛愬彲浠ョ湅鍑猴細娉涘瀷鐨勪笂涓嬭竟鐣屾坊鍔狅紝蹇呴』涓庢硾鍨嬬殑澹版槑鍦ㄤ竴璧?銆?br />4.7 鍏充簬娉涘瀷鏁扮粍瑕佹彁涓€涓嬬湅鍒颁簡寰堝鏂囩珷涓兘浼氭彁璧锋硾鍨嬫暟缁勶紝缁忚繃鏌ョ湅sun鐨勮鏄庢枃妗ｏ紝鍦╦ava涓槸”涓嶈兘鍒涘缓涓€涓‘鍒囩殑娉涘瀷绫诲瀷鐨勬暟缁?rdquo;鐨勩€?br />涔熷氨鏄涓嬮潰鐨勮繖涓緥瀛愭槸涓嶅彲浠ョ殑锛?br />List<String>[] ls = new ArrayList<String>[10];  1鑰屼娇鐢ㄩ€氶厤绗﹀垱寤烘硾鍨嬫暟缁勬槸鍙互鐨勶紝濡備笅闈㈣繖涓緥瀛愶細
List<?>[] ls = new ArrayList<?>[10];  1杩欐牱涔熸槸鍙互鐨勶細
List<String>[] ls = new ArrayList[10];1涓嬮潰浣跨敤Sun鐨勪竴绡囨枃妗ｇ殑涓€涓緥瀛愭潵璇存槑杩欎釜闂锛?br />List<String>[] lsa = new List<String>[10]; // Not really allowed.    Object o = lsa;    Object[] oa = (Object[]) o;    List<Integer> li = new ArrayList<Integer>();    li.add(new Integer(3));    oa[1] = li; // Unsound, but passes run time store check    String s = lsa[1].get(0); // Run-time error: ClassCastException.1234567杩欑鎯呭喌涓嬶紝鐢变簬JVM娉涘瀷鐨勬摝闄ゆ満鍒讹紝鍦ㄨ繍琛屾椂JVM鏄笉鐭ラ亾娉涘瀷淇℃伅鐨勶紝鎵€浠ュ彲浠ョ粰oa[1]璧嬩笂涓€涓狝rrayList鑰屼笉浼氬嚭鐜板紓甯革紝浣嗘槸鍦ㄥ彇鍑烘暟鎹殑鏃跺€欏嵈瑕佸仛涓€娆＄被鍨嬭浆鎹紝鎵€浠ュ氨浼氬嚭鐜癈lassCastException锛屽鏋滃彲浠ヨ繘琛屾硾鍨嬫暟缁勭殑澹版槑锛屼笂闈㈣鐨勮繖绉嶆儏鍐靛湪缂栬瘧鏈熷皢涓嶄細鍑虹幇浠讳綍鐨勮鍛婂拰閿欒锛屽彧鏈夊湪杩愯鏃舵墠浼氬嚭閿欍€?br />鑰屽娉涘瀷鏁扮粍鐨勫０鏄庤繘琛岄檺鍒讹紝瀵逛簬杩欐牱鐨勬儏鍐碉紝鍙互鍦ㄧ紪璇戞湡鎻愮ず浠ｇ爜鏈夌被鍨嬪畨鍏ㄩ棶棰橈紝姣旀病鏈変换浣曟彁绀鸿寮哄緢澶氥€?br />涓嬮潰閲囩敤閫氶厤绗︾殑鏂瑰紡鏄鍏佽鐨?鏁扮粍鐨勭被鍨嬩笉鍙互鏄被鍨嬪彉閲忥紝闄ら潪鏄噰鐢ㄩ€氶厤绗︾殑鏂瑰紡锛屽洜涓哄浜庨€氶厤绗︾殑鏂瑰紡锛屾渶鍚庡彇鍑烘暟鎹槸瑕佸仛鏄惧紡鐨勭被鍨嬭浆鎹㈢殑銆?br />List<?>[] lsa = new List<?>[10]; // OK, array of unbounded wildcard type.    Object o = lsa;    Object[] oa = (Object[]) o;    List<Integer> li = new ArrayList<Integer>();    li.add(new Integer(3));    oa[1] = li; // Correct.    Integer i = (Integer) lsa[1].get(0); // OK 12345675. 鏈€鍚庢湰鏂囦腑鐨勪緥瀛愪富瑕佹槸涓轰簡闃愯堪娉涘瀷涓殑涓€浜涙€濇兂鑰岀畝鍗曚妇鍑虹殑锛屽苟涓嶄竴瀹氭湁鐫€瀹為檯鐨勫彲鐢ㄦ€с€傚彟澶栵紝涓€鎻愬埌娉涘瀷锛岀浉淇″ぇ瀹剁敤鍒版渶澶氱殑灏辨槸鍦ㄩ泦鍚堜腑锛屽叾瀹烇紝鍦ㄥ疄闄呯殑缂栫▼杩囩▼涓紝鑷繁鍙互浣跨敤娉涘瀷鍘荤畝鍖栧紑鍙戯紝涓旇兘寰堝ソ鐨勪繚璇佷唬鐮佽川閲忋€?mdash;———————————————鐗堟潈澹版槑锛氭湰鏂囦负CSDN鍗氫富銆孷ieLei銆嶇殑鍘熷垱鏂囩珷锛岄伒寰?CC 4.0 BY-SA 鐗堟潈鍗忚锛岃浆杞借闄勪笂鍘熸枃鍑哄閾炬帴鍙婃湰澹版槑銆傚師鏂囬摼鎺ワ細https://blog.csdn.net/s10461/article/details/53941091