IndexIdMap (JGAlgo - Parent 0.2.0 API)

```
public interface IndexIdMap
```
A mapping between Graph IDs to IndexGraph indices.
A regular graph contains vertices and edges which are identified by a fixed int IDs. An IndexGraph view is provided by the Graph.indexGraph() method, which is a graph in which all methods are accessed with indices rather than fixed IDs. This interface maps between the indices and the fixed IDs of the graph vertices or edges.
Note that the mapping may change during the graph lifetime, as vertices and edges are added and removed from the graph, and a regular graph IDs are fixed, while a index graph indices are always (0,1,2, ...,verticesNum-1) and (0,1,2, ...,edgesNum-1). The mapping object will be updated automatically in such cases.
The mapping interface is used for both vertices and edges, and we use a unify term element in the documentation to describe both of them. If the mapping was obtained by Graph.indexGraphVerticesMap() it will map between vertices IDs and indices, and if it was obtained by Graph.indexGraphEdgesMap() it will map between edges IDs and indices.

Author:

Barak Ugav

See Also:

IndexGraph

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`int`	`idToIndex(int id)`	Get the index of an element by its ID.
`int`	`indexToId(int index)`	Get the ID of an element by its index.

- Method Detail
  - indexToId
```
int indexToId(int index)
```
    Get the ID of an element by its index.
    Whether this method maps vertices or edges depends if the mapping object was obtained by Graph.indexGraphVerticesMap() or Graph.indexGraphEdgesMap().
    
    Parameters:
    
    index - an index of an element (vertex/edge)
    
    Returns:
    
    the ID of the element
    
    Throws:
    
    IndexOutOfBoundsException - if index is not in range [, elementsNum) where elementsNum is the number of either vertices or edges, depending on the context
  - idToIndex
```
int idToIndex(int id)
```
    Get the index of an element by its ID.
    Whether this method maps vertices or edges depends if the mapping object was obtained by Graph.indexGraphVerticesMap() or Graph.indexGraphEdgesMap().
    
    Parameters:
    
    id - an ID of an element (vertex/edge)
    
    Returns:
    
    the index of the element
    
    Throws:
    
    IndexOutOfBoundsException - if id is not a valid identifier of vertex/edge, depending on the context