alluxio.collections

Class IndexedSet<T>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<T>

alluxio.collections.IndexedSet<T>

Type Parameters:

T - the type of object

All Implemented Interfaces:

Iterable<T>, Collection<T>, Set<T>

@ThreadSafe
public class IndexedSet<T>
extends AbstractSet<T>

A set of objects that are indexed and thus can be queried by specific fields of the object. Different IndexedSet instances may specify different fields to index. The field type must be comparable. The field value must not be changed after an object is added to the set, otherwise, behavior for all operations is not specified. If concurrent adds or removes for objects which are equivalent, but not the same exact object, the behavior is undefined. Therefore, do not add or remove "clones" objects in the IndexedSet.

Example usage: We have a set of puppies:

   class Puppy {
     private final String mName;
     private final long mId;

     public Puppy(String name, long id) {
       mName = name;
       mId = id;
     }

     public String name() {
       return mName;
     }

     public long id() {
       return mId;
     }
   }
 

We want to be able to retrieve the set of puppies via a puppy's id or name, one way is to have two maps like Map<String, Puppy> nameToPuppy and Map<Long, Puppy> idToPuppy, another way is to use a single instance of IndexedSet! First, define the fields to be indexed:

  IndexDefinition idIndex = new IndexDefinition(true) {
     @Override
    Object getFieldValue(Puppy o) {
      return o.id();
    }
  }

  IndexDefinition nameIndex = new IndexDefinition(true) {
     @Override
    Object getFieldValue(Puppy o) {
      return o.name();
    }
  }
 

Then create an IndexedSet and add puppies:

  IndexedSet puppies = new IndexedSet(idIndex, nameIndex);
  puppies.add(new Puppy("sweet", 0));
  puppies.add(new Puppy("heart", 1));
 

Then retrieve the puppy named sweet:

   Puppy sweet = puppies.getFirstByField(nameIndex, "sweet");
 

and retrieve the puppy with id 1:

   Puppy heart = puppies.getFirstByField(idIndex, 1L);
 

Constructor Summary

Constructors

Constructor and Description
IndexedSet(IndexDefinition<T,?> primaryIndexDefinition, IndexDefinition<T,?>... otherIndexDefinitions) Constructs a new IndexedSet instance with at least one field as the index.

Method Summary

Modifier and Type	Method and Description
boolean	add(T object) Adds an object o to the set if there is no other object o2 such that (o == null ? o2 == null : o.equals(o2)).
void	clear() Removes all the entries in this set.
<V> boolean	contains(IndexDefinition<T,V> indexDefinition, V value) Whether there is an object with the specified index field value in the set.
<V> Set<T>	getByField(IndexDefinition<T,V> indexDefinition, V value) Gets a subset of objects with the specified field value.
<V> T	getFirstByField(IndexDefinition<T,V> indexDefinition, V value) Gets the object from the set of objects with the specified field value.
Iterator<T>	iterator() Returns an iterator over the elements in this set.
boolean	remove(Object object) Removes an object from the set.
<V> int	removeByField(IndexDefinition<T,V> indexDefinition, V value) Removes the subset of objects with the specified index field value.
int	size()

Methods inherited from class java.util.AbstractSet

equals, hashCode, removeAll

Methods inherited from class java.util.AbstractCollection

addAll, contains, containsAll, isEmpty, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Set

addAll, contains, containsAll, isEmpty, retainAll, spliterator, toArray, toArray

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

IndexedSet

@SafeVarargs
public IndexedSet(IndexDefinition<T,?> primaryIndexDefinition,
                               IndexDefinition<T,?>... otherIndexDefinitions)

Constructs a new IndexedSet instance with at least one field as the index.

Parameters:

primaryIndexDefinition - at least one field is needed to index the set of objects. This primaryIndexDefinition is used to initialize mPrimaryIndex and is recommended to be unique in consideration of performance.

otherIndexDefinitions - other index definitions to index the set

Method Detail

clear

public void clear()

Removes all the entries in this set. This is an expensive operation, and concurrent adds are permitted.

Specified by:

clear in interface Collection<T>

Specified by:

clear in interface Set<T>

Overrides:

clear in class AbstractCollection<T>

add

public boolean add(T object)

Adds an object o to the set if there is no other object o2 such that (o == null ? o2 == null : o.equals(o2)). If this set already contains the object, the call leaves the set unchanged.

Specified by:

add in interface Collection<T>

Specified by:

add in interface Set<T>

Overrides:

add in class AbstractCollection<T>

Parameters:

object - the object to add

Returns:

true if this set did not already contain the specified element

iterator

public Iterator<T> iterator()

Returns an iterator over the elements in this set. The elements are returned in no particular order. It is to implement Iterable so that users can foreach the IndexedSet directly. Note that the behavior of the iterator is unspecified if the underlying collection is modified while a thread is going through the iterator.

Specified by:

iterator in interface Iterable<T>

Specified by:

iterator in interface Collection<T>

Specified by:

iterator in interface Set<T>

Specified by:

iterator in class AbstractCollection<T>

Returns:

an iterator over the elements in this IndexedSet

contains

public <V> boolean contains(IndexDefinition<T,V> indexDefinition,
                            V value)

Whether there is an object with the specified index field value in the set.

Type Parameters:

V - the field type

Parameters:

indexDefinition - the field index definition

value - the field value

Returns:

true if there is one such object, otherwise false

getByField

public <V> Set<T> getByField(IndexDefinition<T,V> indexDefinition,
                             V value)

Gets a subset of objects with the specified field value. If there is no object with the specified field value, a newly created empty set is returned.

Type Parameters:

V - the field type

Parameters:

indexDefinition - the field index definition

value - the field value to be satisfied

Returns:

the set of objects or an empty set if no such object exists

getFirstByField

public <V> T getFirstByField(IndexDefinition<T,V> indexDefinition,
                             V value)

Gets the object from the set of objects with the specified field value.

Type Parameters:

V - the field type

Parameters:

indexDefinition - the field index definition

value - the field value

Returns:

the object or null if there is no such object

remove

public boolean remove(Object object)

Removes an object from the set.

Specified by:

remove in interface Collection<T>

Specified by:

remove in interface Set<T>

Overrides:

remove in class AbstractCollection<T>

Parameters:

object - the object to remove

Returns:

true if the object is in the set and removed successfully, otherwise false

removeByField

public <V> int removeByField(IndexDefinition<T,V> indexDefinition,
                             V value)

Removes the subset of objects with the specified index field value.

Type Parameters:

V - the field type

Parameters:

indexDefinition - the field index

value - the field value

Returns:

the number of objects removed

size

public int size()

Specified by:

size in interface Collection<T>

Specified by:

size in interface Set<T>

Specified by:

size in class AbstractCollection<T>

Returns:

the number of objects in this indexed set