tachyon.collections

Class IndexedSet<T>

java.lang.Object

tachyon.collections.IndexedSet<T>

All Implemented Interfaces:

Iterable<T>

public class IndexedSet<T>
extends Object
implements Iterable<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.

This class is thread safe.

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:

  FieldIndex idIndex = new FieldIndex {

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	IndexedSet.FieldIndex<T> An interface representing an index for this IndexedSet, each index for this set must implement the interface to define how to get the value of the field chosen as the index.

Constructor Summary

Constructors

Constructor and Description
IndexedSet(IndexedSet.FieldIndex<T> field, IndexedSet.FieldIndex<T>... otherFields) Constructs a new IndexedSet instance with at least one field as the index.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	add(T objToAdd) 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.
boolean	contains(IndexedSet.FieldIndex<T> index, Object value) Whether there is an object with the specified field value in the set.
Set<T>	getByField(IndexedSet.FieldIndex<T> index, Object value) Gets a subset of objects with the specified field value.
T	getFirstByField(IndexedSet.FieldIndex<T> index, Object value) Gets the first 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(T object) Removes an object from the set.
boolean	removeByField(IndexedSet.FieldIndex<T> index, Object value) Removes the subset of objects with the specified field value.
int	size()

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexedSet

public IndexedSet(IndexedSet.FieldIndex<T> field,
          IndexedSet.FieldIndex<T>... otherFields)

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

Parameters:

field - at least one field is needed to index the set of objects

otherFields - other fields to index the set

Method Detail

clear

public void clear()

Removes all the entries in this set.

add

public boolean add(T objToAdd)

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.

Parameters:

objToAdd - the object to add

Returns:

true if the object is successfully added to all indexes, otherwise false

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 behaviour 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>

Returns:

an iterator over the elements in this IndexedSet

contains

public boolean contains(IndexedSet.FieldIndex<T> index,
               Object value)

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

Parameters:

index - the field index

value - the field value

Returns:

true if there is one such object, otherwise false

getByField

public Set<T> getByField(IndexedSet.FieldIndex<T> index,
                Object 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. Otherwise, the returned set is backed up by an internal set, so changes in internal set will be reflected in returned set and vice-versa.

Parameters:

index - the field index

value - the field value to be satisfied

Returns:

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

getFirstByField

public T getFirstByField(IndexedSet.FieldIndex<T> index,
                Object value)

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

Parameters:

index - the field index

value - the field value

Returns:

the object or null if there is no such object

remove

public boolean remove(T object)

Removes an object from the set.

Parameters:

object - the object to remove

Returns:

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

removeByField

public boolean removeByField(IndexedSet.FieldIndex<T> index,
                    Object value)

Removes the subset of objects with the specified field value.

Parameters:

index - the field index

value - the field value

Returns:

true if the objects are removed, otherwise if some objects fail to be removed or no objects are removed, return false

size

public int size()

Returns:

the number of objects in this indexed set (O(1) time)