WebMar 3, 2024 · 先看 HashMap#resize () 中的 newCap 与 newThr 的计算代码。. 当时对情况(1)中的 oldCap >= DEFAULT_INITIAL_CAPACITY 很疑惑,为何要加这个看似多余的限 … WebJan 22, 2024 · Firstly, the oldCap, it is stored existing size of the HashMap (HashTable). If data input into the HashMap at the first time, the oldCap value is 16. This value (capacity) …
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http://geekdaxue.co/read/pluto-@klf4uz/hdewpu WebApr 9, 2024 · newcap := old.cap doublecap := newcap + newcap if cap > doublecap { newcap = cap } else { const threshold = 256 if old.cap < threshold { newcap = doublecap } else { // … goldair ptc wall fan heater gwp-2000a
Java 源码重读系列之 HashMap - 掘金 - 稀土掘金
WebApr 14, 2024 · JAVA里面有HashMap、HashTable、HashSet三种常用的Hash集合,由于经常性的使用,所以想了解一下三种集合的底层实现以及区别,在这里进行总结:一:HashMap和HashTable的区别1.HashTable是线程安全的,而HashMap是线程不安全的。在Java中,我们new一个HashTable出来然后查看源码会发现,里面的实现方法都增加了 ... Web1. threshold = (int)Math.min (initialCapacity * loadFactor, MAX_ARRAY_SIZE + 1); My recollection is that HashMap did, initially, work the same way as Hashtable, but without the (mostly useless) synchronization. And somewhere around JDK 1.4 or 1.5 they changed the behavior to usually just use powers of two, for HashMap. Web1 Essentially, if the old threshold was nonzero, the new one is set to twice its size. Otherwise, if the old threshold was zero (whatever that means, not visible in the code excerpt) we … goldair ptc heater