double r = Math.cos(Math.PI * theta);In order to get around this, people sometimes put static members into an interface and inherit from that interface. This is a bad idea. In fact, it's such a bad idea that there's a name for it: the Constant Interface Antipattern (see Effective Java Item 17). The problem is that a class's use of the static members of another class is a mere implementation detail. When a class implements an interface, it becomes part of the class's public API. Implementation details should not leak into public APIs.
The static import construct allows unqualified access to static members without inheriting from the type containing the static members. Instead, the program imports the members, either individually:
or en masse:import static java.lang.Math.PI;
Once the static members have been imported, they may be used without qualification:import static java.lang.Math.*;
The static import declaration is analogous to the normal import declaration. Where the normal import declaration imports classes from packages, allowing them to be used without package qualification, the static import declaration imports static members from classes, allowing them to be used without class qualification.double r = cos(PI * theta);
So when should you use static import? Very sparingly! Only use it when you'd otherwise be tempted to declare local copies of constants, or to abuse inheritance (the Constant Interface Antipattern). In other words, use it when you require frequent access to static members from one or two classes. If you overuse the static import feature, it can make your program unreadable and unmaintainable, polluting its namespace with all the static members you import. Readers of your code (including you, a few months after you wrote it) will not know which class a static member comes from. Importing all of the static members from a class can be particularly harmful to readability; if you need only one or two members, import them individually. Used appropriately, static import can make your program more readable, by removing the boilerplate of repetition of class names.
鎴戞兂璁$畻鏈轟笓涓氱殑鍏勫紵浠鏍囬鐨勮繖涓や釜璇嶆亹鎬曢兘涓嶉檶鐢熷惂錛佹垜浠細鍦ㄥ緢澶氭枃。涓墤謬簶q欎袱涓瘝錛屼竴鑸槸褰㈠鏌愭煇緋葷粺鐨勪紭鐐癸紝鎴栬呮槸褰㈠鏌愭煇鏋舵瀯鐨勪紭鍔跨瓑絳夈傜敋鑷蟲湁鐨勬椂鍊欐垜浠嚜宸變細璇存垜浠仛鐨勯」鐩湁寰堝ソ鐨?#8220;Extensibility”鍜?#8220;Scalability”銆?/p>
鏇存湁瓚g殑鏄紝榪欎袱涓瘝緇忓父浼氬嚭鐜板湪鎻忚堪鍚屼竴浜嬬墿涓婏紝鑰屼笖鍗曡瘝浼氱揣鎸ㄧ潃銆傛垜浼拌浠ヨ嫳璇負姣嶈鐨勪漢浼氭槑鐧借繖浜岃呭埌搴曟寚鐨勬槸浠涔堟剰鎬濓紝浣嗘槸鍜變滑涓浗鐨処T浜哄+鏄惁鑳芥槑鐧戒簩鑰呭埌搴曟槸浠涔堟剰鎬濆憿錛?/p>
涔嶄竴緲昏瘧榪囨潵錛孍xtensibility鏄?#8220;鍙墿灞曟?#8221;錛岃孲calability涔熷彲浠ョ炕璇戞垚“鍙墿灞曟?#8221;鎴栬?#8220;瑙勬ā鍙墿灞曟?#8221;銆傚弽姝f垜鏄繖涔堢炕璇戠殑銆傝繖涔堜竴鐪嬶紝榪欎簩鑰呬笉鎰忔濆樊涓嶅鍢涳紒閭e共鍢涜繕鐢ㄤ袱涓瘝闃匡紵鍐欎竴涓畻浜嗐?/p>
鑰屽疄闄呭茍闈炲姝わ紝铏界劧Extensibility鍜孲calability緲昏瘧鎴愪腑鏂囧緢鐩歌繎錛屼絾鏄簩鑰呭嵈鏈夌潃鎴劧涓嶅悓鐨勫唴娑點?/p>
Extensibility, 琛ㄦ槑緋葷粺璁捐鐨勫師鍒欙紝鑰冭檻鍒頒簡灝嗘潵瀵圭郴緇熷疄鐜扮殑鏇存敼鍜屽寮恒傚鏋滀竴涓郴緇熸湁寰堝ソ鐨凟xtensibility錛岄偅涔堝綋瀵硅緋葷粺鏌愰儴鍒嗚繘琛屽姛鑳界殑娣誨姞鎴栦慨鏀規椂錛屽嚑涔庝笉浼氬獎鍝嶅埌緋葷粺鐜版湁鐨勫叾浠栭儴鍒嗐?/strong>
Scalability, 琛ㄧず鐨勬槸褰撳涓涓郴緇熺殑浠誨姟閲忔垨宸ヤ綔閲忓鍔犳椂錛岃緋葷粺鑳藉鐢ㄤ竴涓紭闆呯殑鏂瑰紡鏉ュ簲瀵癸紝鑰屼笖杈懼埌浜嗗緢濂界殑鏁堟灉銆傛瘮濡傦紝褰撲竴涓郴緇熷湪澧炲姞浜嗙‖浠惰祫婧愪箣鍚庯紝瀹冪殑鎬ц兘闅忎箣涔熻兘澶熸垚姣斾緥鐨勬彁鍗囷紝榪欏氨琛ㄦ槑榪欎釜緋葷粺鏈夊緢濂界殑Scalability銆?/strong>
閫氳繃涓婇潰鐨勮В閲婏紝鎴戞兂浣犲樊涓嶅鑳芥槑鐧戒簩鑰呭埌搴曡〃鏄庝粈涔堟剰鎬濅簡鍚э紒铏界劧閮芥湁“鎵╁睍鎬?#8221;鐨勬剰鎬濓紝浣嗘槸琛ㄧ幇鐨勬柟闈㈠彲鏄笉鐩稿悓鐨勩?/p>
浜嬪姟鍦烘櫙鏄繖鏍風殑錛?br />
瀵逛簬鍚屼竴涓摱琛屽笎鎴稟鍐呮湁200鍏冿紝鐢茶繘琛屾彁嬈炬搷浣?00鍏冿紝涔欒繘琛岃漿甯愭搷浣?00鍏冨埌B甯愭埛銆傚鏋滀簨鍔℃病鏈夎繘琛岄殧紱誨彲鑳戒細騫跺彂濡備笅闂錛?br />
1銆佺涓綾諱涪澶辨洿鏂幫細棣栧厛鐢叉彁嬈炬椂甯愭埛鍐呮湁200鍏冿紝鍚屾椂涔欒漿甯愪篃鏄?00鍏冿紝鐒跺悗鐢蹭箼鍚屾椂鎿嶄綔錛岀敳鎿嶄綔鎴愬姛鍙栬蛋100鍏冿紝涔欐搷浣滃け璐ュ洖婊氾紝甯愭埛鍐呮渶緇堜負200鍏冿紝榪欐牱鐢茬殑鎿嶄綔琚鐩栨帀浜嗭紝閾惰鎹熷け100鍏冦?br />
2銆佽剰璇伙細鐢插彇嬈?00鍏冩湭鎻愪氦錛屼箼榪涜杞笎鏌ュ埌甯愭埛鍐呭墿鏈?00鍏冿紝榪欐槸鐢叉斁寮冩搷浣滃洖婊氾紝涔欐甯告搷浣滄彁浜わ紝甯愭埛鍐呮渶緇堜負0鍏冿紝涔欒鍙栦簡鐢茬殑鑴忔暟鎹紝瀹㈡埛鎹熷け100鍏冦?br />
3銆佽櫄璇伙細鍜岃剰璇葷被浼鹼紝鏄拡瀵逛簬鎻掑叆鎿嶄綔榪囩▼涓殑璇誨彇闂錛屽涓欏瓨嬈?00鍏冩湭鎻愪氦錛岃繖鏃墮摱琛屽仛鎶ヨ〃榪涜緇熻鏌ヨ甯愭埛涓?00鍏冿紝鐒跺悗涓欐彁浜や簡錛岃繖鏃墮摱琛屽啀緇熻鍙戠幇甯愭埛涓?00鍏冧簡錛屾棤娉曞垽鏂埌搴曚互鍝釜涓哄噯錛?br />
澶у濂藉儚瑙夊緱緇熻榪欎釜涓滆タ鑲畾鏄椂鏃舵洿鏂扮殑錛岃繖縐嶆儏鍐靛緢姝e父錛涗絾鏄鏋滅粺璁℃槸鍦ㄤ竴涓簨鍔′腑鐨勬椂鍊欏氨涓嶆甯鎬簡錛屾瘮濡傛垜浠殑涓涓粺璁″簲鐢ㄩ渶瑕佸皢緇熻緇撴灉鍒嗗埆杈撳嚭鍒扮數鑴戝睆騫曞拰榪滅▼緗戠粶鏌愬彴璁$畻鏈虹殑紓佺洏鏂囦歡涓紝涓轟簡
鎻愰珮鎬ц兘鍜岀敤鎴峰搷搴旀垜浠垎鎴?涓嚎紼嬶紝榪欐椂鍏堝畬鎴愮殑鍜屽悗瀹屾垚鐨勭粺璁℃暟鎹氨鍙兘涓嶄竴鑷達紝鎴戜滑灝變笉鐭ラ亾浠ュ摢涓負鍑嗕簡銆?br />
4銆佷笉鍙噸澶嶈錛氱敳涔欏悓鏃跺紑濮嬮兘鏌ュ埌甯愭埛鍐呬負200鍏冿紝鐢插厛寮濮嬪彇嬈?00鍏冩彁浜わ紝榪欐椂涔欏湪鍑嗗鏈鍚庢洿鏂扮殑鏃跺欏張榪涜浜嗕竴嬈℃煡璇紝鍙戠幇緇撴灉鏄?00鍏冿紝榪欐椂涔欏氨浼氬緢鍥版儜錛屼笉鐭ラ亾璇ュ皢甯愭埛鏀逛負100榪樻槸0銆?br />
鍜岃剰璇葷殑鍖哄埆鏄紝鑴忚鏄鍙栧墠涓浜嬪姟鏈彁浜ょ殑鑴忔暟鎹紝涓嶅彲閲嶅璇繪槸閲嶆柊璇誨彇浜嗗墠涓浜嬪姟宸叉彁浜ょ殑鏁版嵁銆?br />
5銆佺浜岀被涓㈠け鏇存柊錛氭槸涓嶅彲閲嶅璇葷殑涓縐嶇壒渚嬶紝濡備笂錛屼箼涓嶅仛絎簩嬈℃煡璇㈣屾槸鐩存帴鎿嶄綔瀹屾垚錛屽笎鎴峰唴鏈緇堜負100鍏冿紝鐢茬殑鎿嶄綔琚鐩栨帀浜嗭紝閾惰鎹熷け100鍏冦傛劅瑙夊拰絎竴綾諱涪澶辨洿鏂扮被浼箋?/font>
鍦ㄥ涓簨鍔″茍鍙戝仛鏁版嵁搴撴搷浣滅殑鏃跺欙紝濡傛灉娌℃湁鏈夋晥鐨勯伩鍏嶆満鍒訛紝灝變細鍑虹幇縐嶇闂銆傚ぇ浣撲笂鏈変笁縐嶉棶棰橈紝褰掔粨濡備笅錛?br />
1銆佷涪澶辨洿鏂?br />
濡傛灉涓や釜浜嬪姟閮借鏇存柊鏁版嵁搴撲竴涓瓧孌礨錛寈=100
浜嬪姟A 浜嬪姟B
璇誨彇X錛?00
璇誨彇X錛?00
鍐欏叆x錛漍+100
鍐欏叆x錛漍+200
浜嬪姟緇撴潫x=200
浜嬪姟緇撴潫x=300
鏈鍚巟==300
榪欑鎯呭喌浜嬪姟A鐨勬洿鏂板氨琚鐩栨帀浜嗐佷涪澶變簡銆?br />
涓㈠け鏇存柊璇存槑浜嬪姟榪涜鏁版嵁搴撳啓鎿嶄綔鐨勬椂鍊欏彲鑳戒細鍑虹幇鐨勯棶棰樸?br />
2銆佷笉鍙噸澶嶈
涓涓簨鍔″湪鑷繁娌℃湁鏇存柊鏁版嵁搴撴暟鎹殑鎯呭喌錛屽悓涓涓煡璇㈡搷浣滄墽琛屼袱嬈℃垨澶氭鐨勭粨鏋滃簲璇ユ槸涓鑷寸殑錛涘鏋滀笉涓鑷達紝灝辮鏄庝負涓嶅彲閲嶅璇匯?br />
榪樻槸鐢ㄤ笂闈㈢殑渚嬪瓙
浜嬪姟A 浜嬪姟B
璇誨彇X錛?00
璇誨彇X錛?00
璇誨彇X錛?00
鍐欏叆x錛漍+100
璇誨彇X錛?00
浜嬪姟緇撴潫x=200
浜嬪姟緇撴潫x=200
榪欑鎯呭喌浜嬪姟A澶氭璇誨彇x鐨勭粨鏋滃嚭鐜頒簡涓嶄竴鑷達紝鍗充負涓嶅彲閲嶅璇匯?br />
鍐嶆湁涓鎯呭喌灝辨槸騫誨獎
浜嬪姟A璇葷殑鏃跺欒鍑轟簡15鏉¤褰曪紝浜嬪姟B鍦ㄤ簨鍔鎵ц鐨勮繃紼嬩腑鍒犻櫎錛堝鍔狅級浜?鏉★紝浜嬪姟A鍐嶈鐨勬椂鍊欏氨鍙樻垚浜?4錛?6錛夋潯錛岃繖縐嶆儏鍐靛氨鍙仛騫誨獎璇匯?br />
涓嶅彲閲嶅璇昏鏄庝簡鍋氭暟鎹簱璇繪搷浣滅殑鏃跺欏彲鑳戒細鍑虹幇鐨勯棶棰樸?br />
3銆佽剰璇伙紙鏈彁浜よ錛?br />
闃叉涓涓簨鍔¤鍒板彟涓涓簨鍔¤繕娌℃湁鎻愪氦鐨勮褰曘?br />
濡傦細
浜嬪姟A 浜嬪姟B
璇誨彇X錛?00
鍐欏叆x錛漍+100
璇誨彇X錛?00
浜嬪姟鍥炴粴x=100
璇誨彇X錛?00
浜嬪姟緇撴潫x=100
x閿?鎺掍粬閿?琚姞閿佺殑瀵硅薄鍙兘琚寔鏈夐攣鐨勪簨鍔¤鍙栧拰淇敼錛屽叾浠栦簨鍔℃棤娉曞湪璇ュ璞′笂鍔犲叾浠栭攣錛屼篃涓嶈兘璇誨彇鍜屼慨鏀硅瀵硅薄
s閿?鍏變韓閿?琚姞閿佺殑瀵硅薄鍙互琚寔閿佷簨鍔¤鍙栵紝浣嗘槸涓嶈兘琚慨鏀癸紝鍏朵粬浜嬪姟涔熷彲浠ュ湪涓婇潰鍐嶅姞s閿併?br />
灝侀攣鍗忚錛?br />
涓綰у皝閿佸崗璁細
鍦ㄤ簨鍔′慨鏀規暟鎹殑鏃跺欏姞x閿侊紝鐩村埌浜嬪姟緇撴潫錛堟彁浜ゆ垨鑰呭洖婊氾級閲婃斁x閿併備竴綰у皝閿佸崗璁彲浠ユ湁鏁堢殑闃叉涓㈠け鏇存柊錛屼絾鏄笉鑳介槻姝㈣剰璇諱笉鍙噸澶嶈鐨勫嚭鐜般?br />
浜岀駭灝侀攣鍗忚錛?br />
鍦ㄤ竴綰у皝閿佺殑鍩虹涓婁簨鍔¤鏁版嵁鐨勬椂鍊欏姞s閿侊紝璇誨彇涔嬪悗閲婃斁銆備簩綰у皝閿佸崗璁彲浠ラ槻姝涪澶辨洿鏂幫紝鑴忚銆備笉鑳介槻姝笉鍙噸澶嶈銆?br />
涓夌駭灝侀攣鍗忚錛?br />
鍦ㄤ竴綰у皝閿佺殑鍩虹涓婁簨鍔¤鏁版嵁鐨勬椂鍊欏姞s閿侊紝鐩村埌浜嬪姟緇撴潫閲婃斁銆備簩綰у皝閿佸崗璁彲浠ラ槻姝涪澶辨洿鏂幫紝鑴忚錛屼笉鍙噸澶嶈銆?/font>