LightweightGraph (Starlink-UK API)

java.lang.Object
- diva.pod.lwgraph.LightweightGraph

Direct Known Subclasses:

LightweightNetwork
```
public class LightweightGraph
extends Object
```
A light-weight graph data structure. This class requires only that clients implement two very simple interfaces, LWNode and LWEdge (or use the basic implementations provided in this package). Clients add nodes to the graph, and connect them. Clients that want to connect to "ports" on components should use the LightweightNetwork class instead. Clients that want a very fast and compact graph representation should use the low-level classes Topology and Traversal.
Light-weight graphs are hierarchical, in a very simple (and light-weight!) way. Every node can have a "parent" node set for it. Some methods are provided for iterating through the "children" of a given node. Clients that want more complicated or rigid notions of containment can implement it over the top of this API.

Version:

$Revision: 1.10 $

Author:

John Reekie

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`class`	`LightweightGraph.TraversalIterator` The iterator class that is used to iterate over integer arrays of things and map them into objects.

Constructor Summary

Constructors
Constructor and Description

LightweightGraph()
Create a new, empty, light-weight graph

Constructors
Constructor and Description
`LightweightGraph()` Create a new, empty, light-weight graph

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addEdge(LWEdge edge)` Add an edge object to the graph.
`void`	`addNode(LWNode node)` Add a node object to the graph
`void`	`cacheTraversal()` Reconstruct the cache of the topology (this is contained in a pair of Traversal objects).
`void`	`connect(LWEdge edge, LWNode tail, LWNode head)` Connect the given tail and head nodes using the given edge.
`Iterator`	`edges()` Return an iterator over the edges of the graph.
`LWEdge`	`getEdge(int edgeid)` Get the edge with the given id, or null if the edge does not exist.
`int`	`getEdgeCount()` Get the number of edges in this graph
`LWNode`	`getHeadNode(LWEdge edge)` Get the head node of the given edge
`LWNode`	`getNode(int nodeid)` Get the node with the given id, or null if the edge does not exist.
`int`	`getNodeCount()` Get the number of nodes in this graph
`LWNode`	`getParent(LWNode node)` Get the parent node of the given node, or null if the node has no parent (ie is at the root level of the graph).
`LWNode`	`getTailNode(LWEdge edge)` Get the tail node of the given edge
`Topology`	`getTopology()` Get the topology used by this graph.
`Iterator`	`inEdges(LWNode node)` Return an iterator over the edges into the given node.
`void`	`invalidateCache()` Invalidate the cache of the topology.
`Iterator`	`nodes()` Return an iterator over the nodes of the graph.
`Iterator`	`nodes(LWNode parent)` Return an iterator over the nodes that are children of the given node.
`Iterator`	`outEdges(LWNode node)` Return an iterator over the edges out of the given node.
`Iterator`	`predecessors(LWNode node)` Return an iterator over the predecessors of the given node.
`void`	`removeEdge(LWEdge edge)` Remove the given edge.
`void`	`removeNode(LWNode node)` Remove the given node.
`Iterator`	`roots()` Return an iterator over the root nodes of the graph.
`void`	`setHeadNode(LWEdge edge, LWNode head)` Set the head node of the given edge.
`void`	`setParent(LWNode node, LWNode parent)` Set the parent node of the given node.
`void`	`setTailNode(LWEdge edge, LWNode tail)` Set the tail node of the given edge.
`Iterator`	`successors(LWNode node)` Return an iterator over the successors of the given node.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - LightweightGraph
```
public LightweightGraph()
```
    Create a new, empty, light-weight graph
- Method Detail
  - addEdge
```
public void addEdge(LWEdge edge)
```
    Add an edge object to the graph.
  - addNode
```
public void addNode(LWNode node)
```
    Add a node object to the graph
  - cacheTraversal
```
public void cacheTraversal()
```
    Reconstruct the cache of the topology (this is contained in a pair of Traversal objects). This method is automatically called by methods of this class when necessary, so it should not be necessary for the client to call it.
  - connect
```
public void connect(LWEdge edge,
                    LWNode tail,
                    LWNode head)
```
    Connect the given tail and head nodes using the given edge. The nodes must have been added to this graph previously with the addNode() method. The edge must have previously been added to the graph with the addEdge() method. The same two nodes can be connected by more than one edge. The head and tail nodes cannot be null; if you wish to connect just one end of the edge, use the setHead() or setTail() method
  - edges
```
public Iterator edges()
```
    Return an iterator over the edges of the graph. The remove() method is supported, and is equivalent to calling removeEdge() on the current edge. Removing edges by any other means while in an iterator is a very bad idea.
  - getEdge
```
public LWEdge getEdge(int edgeid)
```
    Get the edge with the given id, or null if the edge does not exist.
  - getEdgeCount
```
public int getEdgeCount()
```
    Get the number of edges in this graph
  - getHeadNode
```
public LWNode getHeadNode(LWEdge edge)
```
    Get the head node of the given edge
  - getTopology
```
public Topology getTopology()
```
    Get the topology used by this graph.
  - getNode
```
public LWNode getNode(int nodeid)
```
    Get the node with the given id, or null if the edge does not exist.
  - getNodeCount
```
public int getNodeCount()
```
    Get the number of nodes in this graph
  - getParent
```
public LWNode getParent(LWNode node)
```
    Get the parent node of the given node, or null if the node has no parent (ie is at the root level of the graph).
  - getTailNode
```
public LWNode getTailNode(LWEdge edge)
```
    Get the tail node of the given edge
  - inEdges
```
public Iterator inEdges(LWNode node)
```
    Return an iterator over the edges into the given node.
  - invalidateCache
```
public void invalidateCache()
```
    Invalidate the cache of the topology. This method is automatically called by methods of this class when necessary, so it should not be necessary for the client to call it.
  - nodes
```
public Iterator nodes()
```
    Return an iterator over the nodes of the graph. The remove() method is supported, and is equivalent to calling removeNode() on the most recently returned node. Removing nodes by any other means while in an iterator is not a good idea.
  - nodes
```
public Iterator nodes(LWNode parent)
```
    Return an iterator over the nodes that are children of the given node. The remove() method is supported, and is equivalent to calling setParent(null) on the most recently returned node. NOTE: it does not remove the node from the graph!
  - outEdges
```
public Iterator outEdges(LWNode node)
```
    Return an iterator over the edges out of the given node.
  - predecessors
```
public Iterator predecessors(LWNode node)
```
    Return an iterator over the predecessors of the given node.
  - removeEdge
```
public void removeEdge(LWEdge edge)
```
    Remove the given edge. Will throw an exception of the edge is not in this graph. The edge will of course be disconnected as well as being removed from the graph.
  - removeNode
```
public void removeNode(LWNode node)
```
    Remove the given node. Connected edges will not be affected, it is the client's responsibility to disconnect edges before calling this method. Will throw an exception of the node is not in this graph.
  - roots
```
public Iterator roots()
```
    Return an iterator over the root nodes of the graph. (Where a root is a node that has no predecessor.)
  - setHeadNode
```
public void setHeadNode(LWEdge edge,
                        LWNode head)
```
    Set the head node of the given edge. If the edge is unknown to this graph, it will be added to it. To disconnect the edge from the node, set the node to null.
  - setParent
```
public void setParent(LWNode node,
                      LWNode parent)
```
    Set the parent node of the given node. Both nodes must have previously been added to the graph.
  - setTailNode
```
public void setTailNode(LWEdge edge,
                        LWNode tail)
```
    Set the tail node of the given edge. If the edge is unknown to this graph, it will be added to it. To disconnect the edge from the node, set the node to null.
  - successors
```
public Iterator successors(LWNode node)
```
    Return an iterator over the successors of the given node.

Class LightweightGraph

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

LightweightGraph

Method Detail

addEdge

addNode

cacheTraversal

connect

edges

getEdge

getEdgeCount

getHeadNode

getTopology

getNode

getNodeCount

getParent

getTailNode

inEdges

invalidateCache

nodes

nodes

outEdges

predecessors

removeEdge

removeNode

roots

setHeadNode

setParent

setTailNode

successors