package edu.uci.ics.jung.graph;
import java.util.Collection;
/**
* An interface for a graph which consists of a collection of rooted directed
* acyclic graphs.
*
* @author Joshua O'Madadhain
*/
public interface Forest<V, E> extends DirectedGraph<V, E> {
/**
* Returns a view of this graph as a collection of <code>Tree</code>
* instances.
*
* @return a view of this graph as a collection of <code>Tree</code>s
*/
Collection<Tree<V, E>> getTrees();
/**
* Returns the parent of <code>vertex</code> in this tree. (If
* <code>vertex</code> is the root, returns <code>null</code>.) The parent
* of a vertex is defined as being its predecessor in the (unique) shortest
* path from the root to this vertex. This is a convenience method which is
* equivalent to
* <code>Graph.getPredecessors(vertex).iterator().next()</code>.
*
* @return the parent of <code>vertex</code> in this tree
* @see Graph#getPredecessors(Object)
* @see #getParentEdge(Object)
*/
public V getParent(V vertex);
/**
* Returns the edge connecting <code>vertex</code> to its parent in this
* tree. (If <code>vertex</code> is the root, returns <code>null</code>.)
* The parent of a vertex is defined as being its predecessor in the
* (unique) shortest path from the root to this vertex. This is a
* convenience method which is equivalent to
* <code>Graph.getInEdges(vertex).iterator().next()</code>, and also to
* <code>Graph.findEdge(vertex, getParent(vertex))</code>.
*
* @return the edge connecting <code>vertex</code> to its parent, or
* <code>null</code> if <code>vertex</code> is the root
* @see Graph#getInEdges(Object)
* @see #getParent(Object)
*/
public E getParentEdge(V vertex);
/**
* Returns the children of <code>vertex</code> in this tree. The children of
* a vertex are defined as being the successors of that vertex on the
* respective (unique) shortest paths from the root to those vertices. This
* is syntactic (maple) sugar for <code>getSuccessors(vertex)</code>.
*
* @param vertex
* the vertex whose children are to be returned
* @return the <code>Collection</code> of children of <code>vertex</code> in
* this tree
* @see Graph#getSuccessors(Object)
* @see #getChildEdges(Object)
*/
public Collection<V> getChildren(V vertex);
/**
* Returns the edges connecting <code>vertex</code> to its children in this
* tree. The children of a vertex are defined as being the successors of
* that vertex on the respective (unique) shortest paths from the root to
* those vertices. This is syntactic (maple) sugar for
* <code>getOutEdges(vertex)</code>.
*
* @param vertex
* the vertex whose child edges are to be returned
* @return the <code>Collection</code> of edges connecting
* <code>vertex</code> to its children in this tree
* @see Graph#getOutEdges(Object)
* @see #getChildren(Object)
*/
public Collection<E> getChildEdges(V vertex);
/**
* Returns the number of children that <code>vertex</code> has in this tree.
* The children of a vertex are defined as being the successors of that
* vertex on the respective (unique) shortest paths from the root to those
* vertices. This is syntactic (maple) sugar for
* <code>getSuccessorCount(vertex)</code>.
*
* @param vertex
* the vertex whose child edges are to be returned
* @return the <code>Collection</code> of edges connecting
* <code>vertex</code> to its children in this tree
* @see #getChildEdges(Object)
* @see #getChildren(Object)
* @see Graph#getSuccessorCount(Object)
*/
public int getChildCount(V vertex);
}