java的hashmap高并发问题

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1、java的HashMap高并发问题2010年1月9日114views评论发表评论今天不知为什么服务器卡死了把所有线程的堆栈打印出来是这样的java.util.HashMap.get………………com.labox.common.net.ReceiveWorker.runjava.util.concurrent.ThreadPoolExecutor$Worker.runTaskjava.util.concurrent.ThreadPoolExecutor$Worker.runjava.lang.Thread.run所有线程都是卡死

2、在这里了后来也想不出为什么就用ConcurrentHashMap代替了突然在ibm上发现一编文章是这写的JR33299:6.2.0.1:java.util.HashMap.get()causeshighCPUuseaftermigration<********PASTEMAINBODYCONTENTHERE********>DownloadablefilesAbstractAftermigrationofaWebSphereInterChangeServerrepositoryanddeploymentofthemigrate

3、dartifactstoWebSphereProcessServer,themigratedcontentcauseshighCPUuse.DownloadDescriptionJR33299resolvesthefollowingproblem:ERRORDESCRIPTION:AftermigrationofaWebSphereInterChangeServerrepositoryanddeploymentofthemigratedartifactstoWebSphereProcessServer,themigratedc

4、ontentcauseshighCPUusewhencallingtheBusObjAPI.Thethreaddumpshowsthatmanythreadsarewaiting,whichcausesadegradationinperformance:atjava.util.HashMap.get(HashMap.java:346)atCxCommon.BusinessObject.(BusinessObject.java:277)atCollaboration.BusObj.(BusObj.java

5、:94)UsingConcurrentHashMapinsteadofHashMapcanbypassthisJavaproblem.LOCALFIX:Youcanpossiblyavoidthisproblembyreducingtheconcurrencyofthesystem.USERSAFFECTED:WebSphereProcessServerv6.2.0.1userswhomigrateaWebSphereInterChangeServerrepository.PROBLEMDESCRIPTION:Aftermig

6、rationofaWebSphereInterChangeServerrepositoryanddeploymentofthemigratedartifactstoWebSphereProcessServer,highCPUisseeninjava.util.HashMap.get(),whichiscalledbyanearlyversionoftheBusObjAPI.RECOMMENDATION:NonePROBLEMSUMMARY:java.util.HashMapisnotthread-safeandcancause

7、highCPUusewhenHashMapisusedinaconcurrentsettingwithinsufficientsynchronization.PROBLEMCONCLUSION:Applyingthisinterimfixresolvestheproblem.ThefixforthisAPARistargetedforinclusioninafuturev6.2.0fixpack.好明显，ibm的websphere也遇到这个问题，后来也是把hashMap换成ConcurrentHashMap解决的