LightWeightGSet (Apache Hadoop Common 3.4.1.200-dep-1000 API)

java.lang.Object
- org.apache.hadoop.util.LightWeightGSet<K,E>

Type Parameters:

K - Key type for looking up the elements

E - Element type, which must be (1) a subclass of K, and (2) implementing LightWeightGSet.LinkedElement interface.

All Implemented Interfaces:

java.lang.Iterable<E>, GSet<K,E>

Direct Known Subclasses:

LightWeightCache, LightWeightResizableGSet
```
@Private
public class LightWeightGSet<K,E extends K>
extends java.lang.Object
implements GSet<K,E>
```
A low memory footprint GSet implementation, which uses an array for storing the elements and linked lists for collision resolution. No rehash will be performed. Therefore, the internal array will never be resized. This class does not support null element. This class is not thread safe.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static interface LightWeightGSet.LinkedElement
Elements of LightWeightGSet.

class LightWeightGSet.SetIterator

Nested Classes
Modifier and Type	Class	Description
`static interface`	`LightWeightGSet.LinkedElement`	Elements of `LightWeightGSet`.
`class`	`LightWeightGSet.SetIterator`

Field Summary

Fields
Modifier and Type	Field	Description
`protected LightWeightGSet.LinkedElement[]`	`entries`	An internal array of entries, which are the rows of the hash table.
`protected int`	`hash_mask`	A mask for computing the array index from the hash value of an element.
`protected int`	`modification`	Modification version for fail-fast.
`protected int`	`size`	The size of the set (not the entry array).

Fields inherited from interface org.apache.hadoop.util.GSet
LOG

Constructor Summary

Constructors
Modifier Constructor Description

protected LightWeightGSet()

LightWeightGSet(int recommended_length)

Constructors
Modifier	Constructor	Description
`protected`	`LightWeightGSet()`
	`LightWeightGSet(int recommended_length)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected static int`	`actualArrayLength(int recommended)`
`void`	`clear()`	Clear the set.
`static int`	`computeCapacity(double percentage, java.lang.String mapName)`	Let t = percentage of max memory.
`boolean`	`contains(K key)`	Does this set contain an element corresponding to the given key?
`protected E`	`convert(LightWeightGSet.LinkedElement e)`
`E`	`get(K key)`	Return the stored element which is equal to the given key.
`protected int`	`getIndex(K key)`
`java.util.Iterator<E>`	`iterator()`
`void`	`printDetails(java.io.PrintStream out)`	Print detailed information of this object.
`E`	`put(E element)`	Add/replace an element.
`protected E`	`remove(int index, K key)`	Remove the element corresponding to the key, given key.hashCode() == index.
`E`	`remove(K key)`	Remove the element corresponding to the given key.
`int`	`size()`
`java.lang.String`	`toString()`
`java.util.Collection<E>`	`values()`	Returns a `Collection` view of the values contained in this set.

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

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Field Detail
  - entries
```
protected LightWeightGSet.LinkedElement[] entries
```
    An internal array of entries, which are the rows of the hash table. The size must be a power of two.
  - hash_mask
```
protected int hash_mask
```
    A mask for computing the array index from the hash value of an element.
  - 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
  - LightWeightGSet
```
protected LightWeightGSet()
```
  - LightWeightGSet
```
public LightWeightGSet(int recommended_length)
```
    Parameters:
    
    recommended_length - Recommended size of the internal array.
- Method Detail
  - actualArrayLength
```
protected static int actualArrayLength(int recommended)
```
  - size
```
public int size()
```
    Specified by:
    
    size in interface GSet<K,E extends K>
    
    Returns:
    
    The size of this set.
  - getIndex
```
protected int getIndex(K key)
```
  - convert
```
protected E convert(LightWeightGSet.LinkedElement e)
```
  - get
```
public E get(K key)
```
    Description copied from interface: GSet
    
    Return the stored element which is equal to the given key. This operation is similar to Map.get(Object).
    
    Specified by:
    
    get in interface GSet<K,E extends K>
    
    Parameters:
    
    key - The given key.
    
    Returns:
    
    The stored element if it exists. Otherwise, return null.
  - contains
```
public boolean contains(K key)
```
    Description copied from interface: GSet
    
    Does this set contain an element corresponding to the given key?
    
    Specified by:
    
    contains in interface GSet<K,E extends K>
    
    Parameters:
    
    key - The given key.
    
    Returns:
    
    true if the given key equals to a stored element. Otherwise, return false.
  - put
```
public E put(E element)
```
    Description copied from interface: GSet
    
    Add/replace an element. If the element does not exist, add it to the set. Otherwise, replace the existing element. Note that this operation is similar to Map.put(Object, Object) but is different from Set.add(Object) which does not replace the existing element if there is any.
    
    Specified by:
    
    put in interface GSet<K,E extends K>
    
    Parameters:
    
    element - The element being put.
    
    Returns:
    
    the previous stored element if there is any. Otherwise, return null.
  - remove
```
protected E remove(int index,
                   K key)
```
    Remove the element corresponding to the key, given key.hashCode() == index.
    
    Parameters:
    
    key - key.
    
    index - index.
    
    Returns:
    
    If such element exists, return it. Otherwise, return null.
  - remove
```
public E remove(K key)
```
    Description copied from interface: GSet
    
    Remove the element corresponding to the given key. This operation is similar to Map.remove(Object).
    
    Specified by:
    
    remove in interface GSet<K,E extends K>
    
    Parameters:
    
    key - The key of the element being removed.
    
    Returns:
    
    If such element exists, return it. Otherwise, return null.
  - values
```
public java.util.Collection<E> values()
```
    Description copied from interface: GSet
    
    Returns a Collection view of the values contained in this set. The collection is backed by the set, so changes to the set are reflected in the collection, and vice-versa.
    
    Specified by:
    
    values in interface GSet<K,E extends K>
    
    Returns:
    
    the collection of values.
  - iterator
```
public java.util.Iterator<E> iterator()
```
    Specified by:
    
    iterator in interface java.lang.Iterable<K>
  - 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.
    
    Parameters:
    
    out - out.
  - computeCapacity
```
public static int computeCapacity(double percentage,
                                  java.lang.String mapName)
```
    Let t = percentage of max memory. Let e = round(log_2 t). Then, we choose capacity = 2^e/(size of reference), unless it is outside the close interval [1, 2^30].
    
    Parameters:
    
    mapName - mapName.
    
    percentage - percentage.
    
    Returns:
    
    compute capacity.
  - clear
```
public void clear()
```
    Description copied from interface: GSet
    
    Clear the set.
    
    Specified by:
    
    clear in interface GSet<K,E extends K>

Class LightWeightGSet<K,​E extends K>

Nested Class Summary

Field Summary

Fields inherited from interface org.apache.hadoop.util.GSet

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Field Detail

entries

hash_mask

size

modification

Constructor Detail

LightWeightGSet

LightWeightGSet

Method Detail

actualArrayLength

size

getIndex

convert

get

contains

put

remove

remove

values

iterator

toString

printDetails

computeCapacity

clear

Class LightWeightGSet<K,E extends K>