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這篇文章主要介紹“java非公平鎖是什么”,在日常操作中,相信很多人在java非公平鎖是什么問題上存在疑惑,小編查閱了各式資料,整理出簡單好用的操作方法,希望對大家解答”java非公平鎖是什么”的疑惑有所幫助!接下來,請跟著小編一起來學(xué)習(xí)吧!
1、非公平鎖不能保證鎖的獲取是按照請求鎖的順序進(jìn)行的。這可能會(huì)導(dǎo)致某個(gè)或某些線程永遠(yuǎn)得不到鎖。
2、CPU喚醒線程的費(fèi)用可以降低,整體吞吐效率會(huì)很高。但是可能會(huì)有線程長時(shí)間甚至永遠(yuǎn)得不到鎖,導(dǎo)致餓死。
實(shí)例
/** * Sync object for non-fair locks */ static final class NonfairSync extends Sync { private static final long serialVersionUID = 7316153563782823691L; /** * Performs lock. Try immediate barge, backing up to normal * acquire on failure. */ final void lock() { if (compareAndSetState(0, 1)) setExclusiveOwnerThread(Thread.currentThread()); else acquire(1); } protected final boolean tryAcquire(int acquires) { return nonfairTryAcquire(acquires); } } /** * Sync object for fair locks */ static final class FairSync extends Sync { private static final long serialVersionUID = -3000897897090466540L; final void lock() { acquire(1); } /** * Fair version of tryAcquire. Don't grant access unless * recursive call or no waiters or is first. */ protected final boolean tryAcquire(int acquires) { final Thread current = Thread.currentThread(); int c = getState(); if (c == 0) { if (!hasQueuedPredecessors() && compareAndSetState(0, acquires)) { setExclusiveOwnerThread(current); return true; } } else if (current == getExclusiveOwnerThread()) { int nextc = c + acquires; if (nextc < 0) throw new Error("Maximum lock count exceeded"); setState(nextc); return true; } return false; } }
到此,關(guān)于“java非公平鎖是什么”的學(xué)習(xí)就結(jié)束了,希望能夠解決大家的疑惑。理論與實(shí)踐的搭配能更好的幫助大家學(xué)習(xí),快去試試吧!若想繼續(xù)學(xué)習(xí)更多相關(guān)知識(shí),請繼續(xù)關(guān)注億速云網(wǎng)站,小編會(huì)繼續(xù)努力為大家?guī)砀鄬?shí)用的文章!
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