在ConcurrentHashMap中分割 [英] Segmentation in ConcurrentHashMap

问题描述

  static 
 
我是Java世界的新手，我正在探索ConcurrentHashMap API， final int DEFAULT_INITIAL_CAPACITY = 16; 
 static final float DEFAULT_LOAD_FACTOR = 0.75F; 
 static final int DEFAULT_CONCURRENCY_LEVEL = 16; 
 static final int MAXIMUM_CAPACITY = 1073741824; 
 static final int MAX_SEGMENTS = 65536; 
 static final int RETRIES_BEFORE_LOCK = 2; 
最终细分< K，V> []细分; 
最终分部< K，V> segmentFor（int paramInt）
 {
 return this.segments [（paramInt>>> this.segmentShift& this.segmentMask）]; 
} 
  

ConcurrentHashMap中分段的基本原理及其使用原因是什么？请提供有关分段概念的更多信息。

解决方案

并发哈希映射将其内容分割成段，以减少写入程序锁争用。 / p>

concurrencyLevel 参数定义段的数量。它的默认值是16。

I am a newbie to the world of Java and I was exploring the ConcurrentHashMap API in which I discovered this:

static final int DEFAULT_INITIAL_CAPACITY = 16;
  static final float DEFAULT_LOAD_FACTOR = 0.75F;
  static final int DEFAULT_CONCURRENCY_LEVEL = 16;
  static final int MAXIMUM_CAPACITY = 1073741824;
  static final int MAX_SEGMENTS = 65536;
  static final int RETRIES_BEFORE_LOCK = 2;
  final Segment<K, V>[] segments;
final Segment<K, V> segmentFor(int paramInt)
  {
    return this.segments[(paramInt >>> this.segmentShift & this.segmentMask)];
  }

What are the fundamentals of segmentation in ConcurrentHashMap and why it is used? Please advise more on the segmentation concept.

解决方案

The concurrent hash map divides its contents into segments, to reduce writer lock contention.

The concurrencyLevel parameter defines the number of segments. It's 16 by default.

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