# Class ConcurrentLinkedHashMap.Builder<K,V>

java.lang.Object
org.apache.cayenne.util.concurrentlinkedhashmap.ConcurrentLinkedHashMap.Builder<K,V>

Enclosing class:
  `ConcurrentLinkedHashMap<K,V>`

public static final class ConcurrentLinkedHashMap.Builder<K,V> extends Object
A builder that creates `ConcurrentLinkedHashMap` instances. It provides a flexible approach for constructing customized instances with a named parameter syntax. It can be used in the following manner:

    {
        @code
        ConcurrentMap<Vertex, Set<Edge>> graph = new Builder<Vertex, Set<Edge>>()
                .maximumWeightedCapacity(5000)
                .weigher(Weighers.<Edge> set())
                .build();
    }

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `Builder()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `ConcurrentLinkedHashMap<K,V>`
  `build()`
  Creates a new `ConcurrentLinkedHashMap` instance.
  `ConcurrentLinkedHashMap.Builder<K,V>`
  `catchup(ScheduledExecutorService executor, long delay, TimeUnit unit)`
  Specifies an executor for use in catching up the page replacement policy.
  `ConcurrentLinkedHashMap.Builder<K,V>`
  `concurrencyLevel(int concurrencyLevel)`
  Specifies the estimated number of concurrently updating threads.
  `ConcurrentLinkedHashMap.Builder<K,V>`
  `initialCapacity(int initialCapacity)`
  Specifies the initial capacity of the hash table (default `16`).
  `ConcurrentLinkedHashMap.Builder<K,V>`
  `listener(org.apache.cayenne.util.concurrentlinkedhashmap.EvictionListener<K,V> listener)`
  Specifies an optional listener that is registered for notification when an entry is evicted.
  `ConcurrentLinkedHashMap.Builder<K,V>`
  `maximumWeightedCapacity(int capacity)`
  Specifies the maximum weighted capacity to coerce the map to and may exceed it temporarily.
  `ConcurrentLinkedHashMap.Builder<K,V>`
  `weigher(org.apache.cayenne.util.concurrentlinkedhashmap.Weigher<? super V> weigher)`
  Specifies an algorithm to determine how many the units of capacity a value consumes.

  ### Methods inherited from class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### Builder

    public Builder()

- ## Method Details

  - ### initialCapacity

    public ConcurrentLinkedHashMap.Builder<K,V> initialCapacity(int initialCapacity)
    Specifies the initial capacity of the hash table (default `16`). This is the number of key-value pairs that the hash table can hold before a resize operation is required.
    Parameters:
      `initialCapacity` - the initial capacity used to size the hash table to accommodate this many entries.
    Throws:
      `IllegalArgumentException` - if the initialCapacity is negative

  - ### maximumWeightedCapacity

    public ConcurrentLinkedHashMap.Builder<K,V> maximumWeightedCapacity(int capacity)
    Specifies the maximum weighted capacity to coerce the map to and may exceed it temporarily.
    Parameters:
      `capacity` - the weighted threshold to bound the map by
    Throws:
      `IllegalArgumentException` - if the maximumWeightedCapacity is negative

  - ### concurrencyLevel

    public ConcurrentLinkedHashMap.Builder<K,V> concurrencyLevel(int concurrencyLevel)
    Specifies the estimated number of concurrently updating threads. The implementation performs internal sizing to try to accommodate this many threads (default `16`).
    Parameters:
      `concurrencyLevel` - the estimated number of concurrently updating threads
    Throws:
      `IllegalArgumentException` - if the concurrencyLevel is less than or equal to zero

  - ### listener

    public ConcurrentLinkedHashMap.Builder<K,V> listener(org.apache.cayenne.util.concurrentlinkedhashmap.EvictionListener<K,V> listener)
    Specifies an optional listener that is registered for notification when an entry is evicted.
    Parameters:
      `listener` - the object to forward evicted entries to
    Throws:
      `NullPointerException` - if the listener is null

  - ### weigher

    public ConcurrentLinkedHashMap.Builder<K,V> weigher(org.apache.cayenne.util.concurrentlinkedhashmap.Weigher<? super V> weigher)
    Specifies an algorithm to determine how many the units of capacity a value consumes. The default algorithm bounds the map by the number of key-value pairs by giving each entry a weight of `1`.
    Parameters:
      `weigher` - the algorithm to determine a value's weight
    Throws:
      `NullPointerException` - if the weigher is null

  - ### catchup

    public ConcurrentLinkedHashMap.Builder<K,V> catchup(ScheduledExecutorService executor, long delay, TimeUnit unit)
    Specifies an executor for use in catching up the page replacement policy. The catch-up phase processes both updates to the retention ordering and writes that may trigger an eviction. The delay should be chosen carefully as the map will not automatically evict between executions.

    If unspecified or the executor is shutdown, the catching up will be amortized on user threads during write operations (or during read operations, in the absence of writes).

    A single-threaded `ScheduledExecutorService` should be sufficient for catching up the page replacement policy in many maps.

    Parameters:
      `executor` - the executor to schedule on
      `delay` - the delay between executions
      `unit` - the time unit of the delay parameter
    Throws:
      `NullPointerException` - if the executor or time unit is null
      `IllegalArgumentException` - if the delay is less than or equal to zero

  - ### build

    public ConcurrentLinkedHashMap<K,V> build()
    Creates a new `ConcurrentLinkedHashMap` instance.
    Throws:
      `IllegalStateException` - if the maximum weighted capacity was not set
      `RejectedExecutionException` - if an executor was specified and the catch-up task cannot be scheduled for execution