uk.ac.starlink.table.join

Class RowLink

java.lang.Object

uk.ac.starlink.table.join.RowLink

All Implemented Interfaces:

Comparable<RowLink>

Direct Known Subclasses:

RowLink1, RowLink2, RowLinkN

public abstract class RowLink
extends Object
implements Comparable<RowLink>

Represents an ordered set of RowRefs which are considered in some way linked to each other. Although it doesn't implement the SortedSet interface (being immutable this wouldn't gain you much) its spirit is that of a sorted set - its equals and hashCode methods are implemented such that two RowLinks which contain equivalent groups of RowRef objects are considered the same. This makes RowLink instances suitable for use as keys in hashes that should not contain duplicate entries for duplicate links.

Note: The getRef method must return RowRefs in their natural (Comparable) order.

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
RowLink()

Method Summary

Modifier and Type	Method and Description
int	compareTo(RowLink other) Comparison order compares first table (if present in both objects) first, etc.
static RowLink	createLink(Collection<RowRef> refs) Returns a RowLink instance for a given collection of RowRefs.
boolean	equals(Object o) Assesses equality.
abstract RowRef	getRef(int i) Returns the ith row ref in this ordered sequence of refs.
int	hashCode() Returns a hash code which is consistent with the equals method.
abstract int	size() Returns the number of rows linked by this object.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

RowLink

public RowLink()

Method Detail

size

public abstract int size()

Returns the number of rows linked by this object.

Returns:

number of RowRefs

getRef

public abstract RowRef getRef(int i)

Returns the i^th row ref in this ordered sequence of refs. The sequence must be as defined by RowRef.compareTo.

Parameters:

i - index

Returns:

RowRef at i

equals

public boolean equals(Object o)

Assesses equality. Two RowLink objects are equal if they contain equivalent sets of RowRefs.

Overrides:

equals in class Object

hashCode

public int hashCode()

Returns a hash code which is consistent with the equals method. Since RowLinks are immutable, this is only calculated once, for efficiency.

Overrides:

hashCode in class Object

compareTo

public int compareTo(RowLink other)

Comparison order compares first table (if present in both objects) first, etc.

Specified by:

compareTo in interface Comparable<RowLink>

toString

public String toString()

Overrides:

toString in class Object

createLink

public static RowLink createLink(Collection<RowRef> refs)

Returns a RowLink instance for a given collection of RowRefs. This may be more efficient than using the RowLinkN constructor.

Parameters:

refs - row refs

Returns:

row link containing given refs