Package uk.ac.starlink.table.join

Class RowLink

  • All Implemented Interfaces:
    java.lang.Comparable<RowLink>
    Direct Known Subclasses:
    RowLink1, RowLink2, RowLinkN
    public abstract class RowLink
extends java.lang.Object
implements java.lang.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 Description
      RowLink()  

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      int compareTo​(RowLink other)
      Comparison order compares first table (if present in both objects) first, etc.
      static RowLink createLink​(java.util.Collection<RowRef> refs)
      Returns a RowLink instance for a given collection of RowRefs.
      boolean equals​(java.lang.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.
      java.lang.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 ith 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​(java.lang.Object o)
        Assesses equality. Two RowLink objects are equal if they contain equivalent sets of RowRefs.
        Overrides:
        equals in class java.lang.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 java.lang.Object

      • compareTo

        public int compareTo​(RowLink other)
        Comparison order compares first table (if present in both objects) first, etc.
        Specified by:
        compareTo in interface java.lang.Comparable<RowLink>

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • createLink

        public static RowLink createLink​(java.util.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