Java Lock 接口

Lock

Java AQS

java.util.concurrent.locks.AbstractQueuedSynchronizer 鎶借薄绫伙紝绠€绉?AQS 锛屾槸涓€涓敤浜庢瀯寤洪攣鍜屽悓姝ュ鍣ㄧ殑鍚屾鍣ㄣ€備簨瀹炰笂concurrent 鍖呭唴璁稿绫婚兘鏄熀浜?AQS 鏋勫缓銆備緥濡?ReentrantLock锛孲emaphore锛孋ountDownLatch锛孯eentrantReadWriteLock锛岀瓑銆侫QS 瑙ｅ喅浜嗗湪瀹炵幇鍚屾瀹瑰櫒鏃惰璁＄殑澶ч噺缁嗚妭闂銆?/p>

AQS 浣跨敤涓€涓?FIFO 鐨勯槦鍒楄〃绀烘帓闃熺瓑寰呴攣鐨勭嚎绋嬶紝闃熷垪澶磋妭鐐圭О浣溾€滃摠鍏佃妭鐐光€濇垨鑰呪€滃搼鑺傜偣鈥濓紝瀹冧笉涓庝换浣曠嚎绋嬪叧鑱斻€傚叾浠栫殑鑺傜偣涓庣瓑寰呯嚎绋嬪叧鑱旓紝姣忎釜鑺傜偣缁存姢涓€涓瓑寰呯姸鎬?waitStatus 銆?/p>

• Java骞跺彂涔婣QS璇﹁В

浠€涔堟槸 Java Lock 鎺ュ彛锛?/h2>

java.util.concurrent.locks.Lock 鎺ュ彛锛屾瘮 synchronized 鎻愪緵鏇村叿鎷撳睍琛岀殑閿佹搷浣溿€傚畠鍏佽鏇寸伒娲荤殑缁撴瀯锛屽彲浠ュ叿鏈夊畬鍏ㄤ笉鍚岀殑鎬ц川锛屽苟涓斿彲浠ユ敮鎸佸涓浉鍏崇被鐨勬潯浠跺璞°€傚畠鐨勪紭鍔挎湁锛?/p>

• 鍙互浣块攣鏇村叕骞炽€?/li>
• 鍙互浣跨嚎绋嬪湪绛夊緟閿佺殑鏃跺€欏搷搴斾腑鏂€?/li>
• 鍙互璁╃嚎绋嬪皾璇曡幏鍙栭攣锛屽苟鍦ㄦ棤娉曡幏鍙栭攣鐨勬椂鍊欑珛鍗宠繑鍥炴垨鑰呯瓑寰呬竴娈垫椂闂淬€?/li>
• 鍙互鍦ㄤ笉鍚岀殑鑼冨洿锛屼互涓嶅悓鐨勯『搴忚幏鍙栧拰閲婃斁閿併€?/li>

浠€涔堟槸鍙噸鍏ラ攣锛圧eentrantLock锛夛紵

synchronized銆丷eentrantLock 閮芥槸鍙噸鍏ョ殑閿侊紝鍙噸鍏ラ攣鐩稿鏉ヨ绠€鍖栦簡骞跺彂缂栫▼鐨勫紑鍙戙€?/p>

鍏充簬 ReentrantLock 绫伙紝璇︾粏鐨勬簮鐮佽В鏋愶紝鍙互鐪嬬湅 銆娿€愭纾?Java 骞跺彂銆戔€斺€?J.U.C 涔嬮噸鍏ラ攣锛歊eentrantLock銆?銆?/p>

绠€鍗曟潵璇达紝ReenTrantLock 鐨勫疄鐜版槸涓€绉嶈嚜鏃嬮攣锛岄€氳繃寰幆璋冪敤 CAS 鎿嶄綔鏉ュ疄鐜板姞閿併€傚畠鐨勬€ц兘姣旇緝濂戒篃鏄洜涓洪伩鍏嶄簡浣跨嚎绋嬭繘鍏ュ唴鏍告€佺殑闃诲鐘舵€併€傛兂灏藉姙娉曢伩鍏嶇嚎绋嬭繘鍏ュ唴鏍哥殑闃诲鐘舵€佹槸鎴戜滑鍘诲垎鏋愬拰鐞嗚В閿佽璁＄殑鍏抽敭閽ュ寵銆?/p>

馃 synchronized 鍜?ReentrantLock 寮傚悓锛?/strong>

• 鐩稿悓鐐?
  • 閮藉疄鐜颁簡澶氱嚎绋嬪悓姝ュ拰鍐呭瓨鍙鎬ц涔夈€?/li>
  • 閮芥槸鍙噸鍏ラ攣銆?/li>
• 涓嶅悓鐐?

  • 鍚屾瀹炵幇鏈哄埗涓嶅悓

    • synchronized 閫氳繃 Java 瀵硅薄澶撮攣鏍囪鍜?Monitor 瀵硅薄瀹炵幇鍚屾銆?/li>
    • ReentrantLock 閫氳繃CAS銆丄QS锛圓bstractQueuedSynchronizer锛夊拰 LockSupport锛堢敤浜庨樆濉炲拰瑙ｉ櫎闃诲锛夊疄鐜板悓姝ャ€?/li>

  • 鍙鎬у疄鐜版満鍒朵笉鍚?/p>

    • synchronized 渚濊禆 JVM 鍐呭瓨妯″瀷淇濊瘉鍖呭惈鍏变韩鍙橀噺鐨勫绾跨▼鍐呭瓨鍙鎬с€?/li>
    • ReentrantLock 閫氳繃 ASQ 鐨?volatile state 淇濊瘉鍖呭惈鍏变韩鍙橀噺鐨勫绾跨▼鍐呭瓨鍙鎬с€?/li>

  • 浣跨敤鏂瑰紡涓嶅悓

    • synchronized 鍙互淇グ瀹炰緥鏂规硶锛堥攣浣忓疄渚嬪璞★級銆侀潤鎬佹柟娉曪紙閿佷綇绫诲璞★級銆佷唬鐮佸潡锛堟樉绀烘寚瀹氶攣瀵硅薄锛夈€?/li>
    • ReentrantLock 鏄剧ず璋冪敤 tryLock 鍜?lock 鏂规硶锛岄渶瑕佸湪 finally 鍧椾腑閲婃斁閿併€?/li>

  • 鍔熻兘涓板瘜绋嬪害涓嶅悓

    • synchronized 涓嶅彲璁剧疆绛夊緟鏃堕棿銆佷笉鍙涓柇锛坕nterrupted锛夈€?/li>
    • ReentrantLock 鎻愪緵鏈夐檺鏃堕棿绛夊€欓攣锛堣缃繃鏈熸椂闂达級銆佸彲涓柇閿侊紙lockInterruptibly锛夈€乧ondition锛堟彁渚?await銆乧ondition锛堟彁渚?await銆乻ignal 绛夋柟娉曪級绛変赴瀵屽姛鑳?/li>

  • 閿佺被鍨嬩笉鍚?/p>

    • synchronized 鍙敮鎸侀潪鍏钩閿併€?/li>
    • ReentrantLock 鎻愪緵鍏钩閿佸拰闈炲叕骞抽攣瀹炵幇銆傚綋鐒讹紝鍦ㄥぇ閮ㄥ垎鎯呭喌涓嬶紝闈炲叕骞抽攣鏄珮鏁堢殑閫夋嫨銆?/li>

鍦?synchronized 浼樺寲浠ュ墠锛屽畠鐨勬€ц兘鏄瘮 ReenTrantLock 宸緢澶氱殑锛屼絾鏄嚜浠?synchronized 寮曞叆浜嗗亸鍚戦攣锛岃交閲忕骇閿侊紙鑷棆閿侊級鍚庯紝涓よ€呯殑鎬ц兘灏卞樊涓嶅浜嗭紝鍦ㄤ袱绉嶆柟娉曢兘鍙敤鐨勬儏鍐典笅锛屽畼鏂圭敋鑷冲缓璁娇鐢?synchronized 銆?/p>

骞朵笖锛屽疄闄呬唬鐮佸疄鎴樹腑锛屽彲鑳界殑浼樺寲鍦烘櫙鏄紝閫氳繃璇诲啓鍒嗙锛岃繘涓€姝ユ€ц兘鐨勬彁鍗囷紝鎵€浠ヤ娇鐢?ReentrantReadWriteLock 銆傪煒?/p>

ReadWriteLock 鏄粈涔堬紵

ReadWriteLock 锛岃鍐欓攣鏄紝鐢ㄦ潵鎻愬崌骞跺彂绋嬪簭鎬ц兘鐨勯攣鍒嗙鎶€鏈殑 Lock 瀹炵幇绫汇€傚彲浠ョ敤浜?鈥滃璇诲皯鍐欌€?鐨勫満鏅紝璇诲啓閿佹敮鎸佸涓鎿嶄綔骞跺彂鎵ц锛屽啓鎿嶄綔鍙兘鐢变竴涓嚎绋嬫潵鎿嶄綔銆?/p>

ReadWriteLock 瀵瑰悜鏁版嵁缁撴瀯鐩稿涓嶉绻佸湴鍐欏叆锛屼絾鏄湁澶氫釜浠诲姟瑕佺粡甯歌鍙栬繖涓暟鎹粨鏋勭殑杩欑被鎯呭喌杩涜浜嗕紭鍖栥€俁eadWriteLock 浣垮緱浣犲彲浠ュ悓鏃舵湁澶氫釜璇诲彇鑰咃紝鍙瀹冧滑閮戒笉璇曞浘鍐欏叆鍗冲彲銆傚鏋滃啓閿佸凡缁忚鍏朵粬浠诲姟鎸佹湁锛岄偅涔堜换浣曡鍙栬€呴兘涓嶈兘璁块棶锛岀洿鑷宠繖涓啓閿佽閲婃斁涓烘銆?/p>

ReadWriteLock 瀵圭▼搴忔€ц兘鐨勬彁楂樹富瑕佸彈鍒朵簬濡備笅鍑犱釜鍥犵礌锛?/p>

1. 鏁版嵁琚鍙栫殑棰戠巼涓庤淇敼鐨勯鐜囩浉姣旇緝鐨勭粨鏋溿€?/li>
2. 璇诲彇鍜屽啓鍏ョ殑鏃堕棿
3. 鏈夊灏戠嚎绋嬬珵浜?/li>
4. 鏄惁鍦ㄥ澶勭悊鏈哄櫒涓婅繍琛?/li>

ReadWriteLock 鐨勬簮鐮佽В鏋愶紝鍙互鐪嬬湅 銆娿€愭纾?Java 骞跺彂銆戔€斺€?J.U.C 涔嬭鍐欓攣锛歊eentrantReadWriteLock銆?銆?/p>

Condition 鏄粈涔堬紵

鍦ㄦ病鏈?Lock 涔嬪墠锛屾垜浠娇鐢?synchronized 鏉ユ帶鍒跺悓姝ワ紝閰嶅悎 Object 鐨?#wait()銆?code>#notify() 绛変竴绯诲垪鏂规硶鍙互瀹炵幇绛夊緟 / 閫氱煡妯″紡銆傚湪 Java SE 5 鍚庯紝Java 鎻愪緵浜?Lock 鎺ュ彛锛岀浉瀵逛簬 synchronized 鑰岃█锛孡ock 鎻愪緵浜嗘潯浠?Condition 锛屽绾跨▼鐨勭瓑寰呫€佸敜閱掓搷浣滄洿鍔犺缁嗗拰鐏垫椿銆備笅鍥炬槸 Condition 涓?Object 鐨勭洃瑙嗗櫒鏂规硶鐨勫姣旓紙鎽樿嚜銆奐ava骞跺彂缂栫▼鐨勮壓鏈€嬶級锛?/p>

Condition 涓?Object 鐨勭洃瑙嗗櫒鏂规硶鐨勫姣?/div>

Condition 涓?Object 鐨勭洃瑙嗗櫒鏂规硶鐨勫姣?

• Condition 鐨勬簮鐮侊紝鍙互鐪嬬湅 銆娿€愭纾?Java 骞跺彂銆戔€斺€?J.U.C 涔?Condition銆?銆?/li>

馃 鐢ㄤ笁涓嚎绋嬫寜椤哄簭寰幆鎵撳嵃 abc 涓変釜瀛楁瘝锛屾瘮濡?abcabcabc 锛?/strong>

• 浣跨敤 Lock + Condition 鏉ュ疄鐜般€傚叿浣撲唬鐮侊紝鍙傜湅 銆婄敤涓変釜绾跨▼鎸夐『搴忓惊鐜墦鍗?abc 涓変釜瀛楁瘝锛屾瘮濡?abcabcabc銆?銆?/li>

LockSupport 鏄粈涔堬紵

LockSupport 鏄?JDK 涓瘮杈冨簳灞傜殑绫伙紝鐢ㄦ潵鍒涘缓閿佸拰鍏朵粬鍚屾宸ュ叿绫荤殑鍩烘湰绾跨▼闃诲銆?/p>

• Java 閿佸拰鍚屾鍣ㄦ鏋剁殑鏍稿績 AQS(AbstractQueuedSynchronizer)锛屽氨鏄€氳繃璋冪敤 LockSupport#park()鍜?LockSupport#unpark() 鏂规硶锛屾潵瀹炵幇绾跨▼鐨勯樆濉炲拰鍞ら啋鐨勩€?/p>

• LockSupport 寰堢被浼间簬浜屽厓淇″彿閲?鍙湁 1 涓鍙瘉鍙緵浣跨敤)锛屽鏋滆繖涓鍙繕娌℃湁琚崰鐢紝褰撳墠绾跨▼鑾峰彇璁稿彲骞剁户缁墽琛岋紱濡傛灉璁稿彲宸茬粡琚崰鐢紝褰撳墠绾跨▼闃诲锛岀瓑寰呰幏鍙栬鍙€?/p>

• 銆奐ava 骞跺彂缂栫▼ 鈥斺€?LockSupport銆?甯﹂儴鍒嗘簮鐮佽В鏋愩€?/p>