Lab3Help

Interface Path<E>

All Known Implementing Classes:

External

public interface Path<E>

A path is a sequence of nodes describing how to get from one node to another in a graph. A node is represented by its name (a String). A node cannot occur more than once in a single path. The path is initialized by a call to computePath() after which the relevant information can be retrieved using the methods getPath() and getPathLength().

A class implementing Path could perhaps be used as follows:

  Lab3File f = new Lab3File();
  List<BStop>      stops = f.readStops("stops-gbg.txt");
  List<BLineTable> lines = f.readLines("lines-gbg.txt");
  Path<String> p = new MyPath(stops, lines);
  p.computePath("Chalmers","Angered");
  System.out.println("Distance: " + p.getPathLength());
  p.computePath("Chalmers","GuldHeden");
  System.out.println("Distance: " + p.getPathLength());

Method Summary

Modifier and Type	Method and Description
void	computePath(E from, E to) Computes the path from from to to (if any).
Iterator<E>	getPath() Returns an iterator over the nodes in the path.
int	getPathLength() Returns the length of the computed path, that is, the sum of the weights of each arc on the path.

Method Detail

computePath

void computePath(E from,
                 E to)

Computes the path from from to to (if any). Path information can be retrieved by subsequent calls to getPath() and getPathLength(). It must be possible to call this method any number of times.

Precondition: The underlying graph must not contain any negative edge weights.

getPath

Iterator<E> getPath()

Returns an iterator over the nodes in the path.

If a path has been found the first node in the iterator is the argument from passed to computePath and the last node is to.

If no path was found or if no call to computePath has been made the iterator is empty.

Returns:

An iterator over the computed path.

getPathLength

int getPathLength()

Returns the length of the computed path, that is, the sum of the weights of each arc on the path.

If no path was found the return value is an arbitrary integer. It is appropriate but not required to return a special value such as -1 in this case.

Returns:

The length of the computed path.