LightWeightHashSet (Apache Hadoop HDFS 3.4.1.100-eep-941 API)

java.lang.Object
- org.apache.hadoop.hdfs.util.LightWeightHashSet<T>

All Implemented Interfaces:

java.lang.Iterable<T>, java.util.Collection<T>

Direct Known Subclasses:

LightWeightLinkedSet
```
public class LightWeightHashSet<T>
extends java.lang.Object
implements java.util.Collection<T>
```
A low memory linked hash set implementation, which uses an array for storing the elements and linked lists for collision resolution. This class does not support null element. This class is not thread safe.

Field Summary

Fields
Modifier and Type	Field	Description
`protected static float`	`DEFAULT_MAX_LOAD_FACTOR`
`protected static float`	`DEFAUT_MIN_LOAD_FACTOR`
`protected org.apache.hadoop.hdfs.util.LightWeightHashSet.LinkedElement<T>[]`	`entries`	An internal array of entries, which are the rows of the hash table.
`protected static int`	`MINIMUM_CAPACITY`
`protected int`	`modification`	Modification version for fail-fast.
`protected int`	`size`	The size of the set (not the entry array).

Constructor Summary

Constructors
Constructor	Description
`LightWeightHashSet()`
`LightWeightHashSet(int minCapacity)`
`LightWeightHashSet(int initCapacity, float maxLoadFactor, float minLoadFactor)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`add(T element)`	Add given element to the hash table.
`boolean`	`addAll(java.util.Collection<? extends T> toAdd)`	All all elements in the collection.
`protected boolean`	`addElem(T element)`	Add given element to the hash table
`void`	`clear()`	Clear the set.
`boolean`	`contains(java.lang.Object key)`	Check if the set contains given element
`boolean`	`containsAll(java.util.Collection<?> c)`
`protected void`	`expandIfNecessary()`	Checks if we need to expand, and expands if necessary.
`int`	`getCapacity()`	Return the current capacity (for testing).
`protected T`	`getContainedElem(int index, T key, int hashCode)`	Check if the set contains given element at given index.
`T`	`getElement(T key)`	Return the element in this set which is equal to the given key, if such an element exists.
`protected int`	`getIndex(int hashCode)`	Get index in the internal table for a given hash.
`boolean`	`isEmpty()`	Check if the set is empty.
`java.util.Iterator<T>`	`iterator()`
`java.util.List<T>`	`pollAll()`	Remove all elements from the set and return them.
`java.util.List<T>`	`pollN(int n)`	Remove and return n elements from the hashtable.
`T[]`	`pollToArray(T[] array)`	Get array.length elements from the set, and put them into the array.
`void`	`printDetails(java.io.PrintStream out)`	Print detailed information of this object.
`boolean`	`remove(java.lang.Object key)`	Remove the element corresponding to the key.
`boolean`	`removeAll(java.util.Collection<?> c)`
`protected org.apache.hadoop.hdfs.util.LightWeightHashSet.LinkedElement<T>`	`removeElem(T key)`	Remove the element corresponding to the key, given key.hashCode() == index.
`boolean`	`retainAll(java.util.Collection<?> c)`
`protected void`	`shrinkIfNecessary()`	Checks if we need to shrink, and shrinks if necessary.
`int`	`size()`	Return the number of stored elements.
`java.lang.Object[]`	`toArray()`
`<U> U[]`	`toArray(U[] a)`
`java.lang.String`	`toString()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection
equals, hashCode, parallelStream, removeIf, spliterator, stream, toArray

Methods inherited from interface java.lang.Iterable
forEach

- Field Detail
  - DEFAULT_MAX_LOAD_FACTOR
```
protected static final float DEFAULT_MAX_LOAD_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAUT_MIN_LOAD_FACTOR
```
protected static final float DEFAUT_MIN_LOAD_FACTOR
```
    See Also:
    
    Constant Field Values
  - MINIMUM_CAPACITY
```
protected static final int MINIMUM_CAPACITY
```
    See Also:
    
    Constant Field Values
  - entries
```
protected org.apache.hadoop.hdfs.util.LightWeightHashSet.LinkedElement<T>[] entries
```
    An internal array of entries, which are the rows of the hash table. The size must be a power of two.
  - size
```
protected int size
```
    The size of the set (not the entry array).
  - modification
```
protected int modification
```
    Modification version for fail-fast.
    
    See Also:
    
    ConcurrentModificationException
- Constructor Detail
  - LightWeightHashSet
```
public LightWeightHashSet(int initCapacity,
                          float maxLoadFactor,
                          float minLoadFactor)
```
    Parameters:
    
    initCapacity - Recommended size of the internal array.
    
    maxLoadFactor - used to determine when to expand the internal array
    
    minLoadFactor - used to determine when to shrink the internal array
  - LightWeightHashSet
```
public LightWeightHashSet()
```
  - LightWeightHashSet
```
public LightWeightHashSet(int minCapacity)
```
- Method Detail
  - isEmpty
```
public boolean isEmpty()
```
    Check if the set is empty.
    
    Specified by:
    
    isEmpty in interface java.util.Collection<T>
    
    Returns:
    
    true is set empty, false otherwise
  - getCapacity
```
public int getCapacity()
```
    Return the current capacity (for testing).
  - size
```
public int size()
```
    Return the number of stored elements.
    
    Specified by:
    
    size in interface java.util.Collection<T>
  - getIndex
```
protected int getIndex(int hashCode)
```
    Get index in the internal table for a given hash.
  - contains
```
public boolean contains(java.lang.Object key)
```
    Check if the set contains given element
    
    Specified by:
    
    contains in interface java.util.Collection<T>
    
    Returns:
    
    true if element present, false otherwise.
  - getElement
```
public T getElement(T key)
```
    Return the element in this set which is equal to the given key, if such an element exists. Otherwise returns null.
  - getContainedElem
```
protected T getContainedElem(int index,
                             T key,
                             int hashCode)
```
    Check if the set contains given element at given index. If it does, return that element.
    
    Returns:
    
    the element, or null, if no element matches
  - addAll
```
public boolean addAll(java.util.Collection<? extends T> toAdd)
```
    All all elements in the collection. Expand if necessary.
    
    Specified by:
    
    addAll in interface java.util.Collection<T>
    
    Parameters:
    
    toAdd - - elements to add.
    
    Returns:
    
    true if the set has changed, false otherwise
  - add
```
public boolean add(T element)
```
    Add given element to the hash table. Expand table if necessary.
    
    Specified by:
    
    add in interface java.util.Collection<T>
    
    Returns:
    
    true if the element was not present in the table, false otherwise
  - addElem
```
protected boolean addElem(T element)
```
    Add given element to the hash table
    
    Returns:
    
    true if the element was not present in the table, false otherwise
  - remove
```
public boolean remove(java.lang.Object key)
```
    Remove the element corresponding to the key.
    
    Specified by:
    
    remove in interface java.util.Collection<T>
    
    Returns:
    
    If such element exists, return true. Otherwise, return false.
  - removeElem
```
protected org.apache.hadoop.hdfs.util.LightWeightHashSet.LinkedElement<T> removeElem(T key)
```
    Remove the element corresponding to the key, given key.hashCode() == index.
    
    Returns:
    
    If such element exists, return true. Otherwise, return false.
  - pollN
```
public java.util.List<T> pollN(int n)
```
    Remove and return n elements from the hashtable. The order in which entries are removed is unspecified, and and may not correspond to the order in which they were inserted.
    
    Returns:
    
    first element
  - pollAll
```
public java.util.List<T> pollAll()
```
    Remove all elements from the set and return them. Clear the entries.
  - pollToArray
```
public T[] pollToArray(T[] array)
```
    Get array.length elements from the set, and put them into the array.
  - shrinkIfNecessary
```
protected void shrinkIfNecessary()
```
    Checks if we need to shrink, and shrinks if necessary.
  - expandIfNecessary
```
protected void expandIfNecessary()
```
    Checks if we need to expand, and expands if necessary.
  - iterator
```
public java.util.Iterator<T> iterator()
```
    Specified by:
    
    iterator in interface java.util.Collection<T>
    
    Specified by:
    
    iterator in interface java.lang.Iterable<T>
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - printDetails
```
public void printDetails(java.io.PrintStream out)
```
    Print detailed information of this object.
  - clear
```
public void clear()
```
    Clear the set. Resize it to the original capacity.
    
    Specified by:
    
    clear in interface java.util.Collection<T>
  - toArray
```
public java.lang.Object[] toArray()
```
    Specified by:
    
    toArray in interface java.util.Collection<T>
  - toArray
```
public <U> U[] toArray(U[] a)
```
    Specified by:
    
    toArray in interface java.util.Collection<T>
  - containsAll
```
public boolean containsAll(java.util.Collection<?> c)
```
    Specified by:
    
    containsAll in interface java.util.Collection<T>
  - removeAll
```
public boolean removeAll(java.util.Collection<?> c)
```
    Specified by:
    
    removeAll in interface java.util.Collection<T>
  - retainAll
```
public boolean retainAll(java.util.Collection<?> c)
```
    Specified by:
    
    retainAll in interface java.util.Collection<T>

Class LightWeightHashSet<T>

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Collection

Methods inherited from interface java.lang.Iterable

Field Detail

DEFAULT_MAX_LOAD_FACTOR

DEFAUT_MIN_LOAD_FACTOR

MINIMUM_CAPACITY

entries

size

modification

Constructor Detail

LightWeightHashSet

LightWeightHashSet

LightWeightHashSet

Method Detail

isEmpty

getCapacity

size

getIndex

contains

getElement

getContainedElem

addAll

add

addElem

remove

removeElem

pollN

pollAll

pollToArray

shrinkIfNecessary

expandIfNecessary

iterator

toString

printDetails

clear

toArray

toArray

containsAll

removeAll

retainAll