A simple graph program

1. Dynamically add or delete vertices in the graph;
2. Dynamically add, edit or delete a weighted edge in the graph;
3. Show the contents of the current graph;
4. Show a topological ordering in the graph;
5. Given one vertex as a starting vertex, show the shortest path from this starting vertex to the other vertices in the graph;

Add a vertex vertex {v}
Add vertex A: vertex A

Delete a vertex -vertex {v}
Delete vertex A: -vertex A

Add an edge edge {weight} {v1} {v2}
Add an edge from vertex A to vertex B, the weight is 8: edge 8 A B

Modify an edge weight {weight} {v1} {v2}
Change the weight of the edge AB to 5: weight 5 A B

Delete an edge -edge {v1} {v2}
Delete the edge AB: -edge A B

Show the contents contents
Show the contents: contents

Show the topological ordering
topo

Show the topological ordering of the current graph: topo
Show the shortest paths from a vertex

path {v} Show the shortest path from vertex A to other vertices: path A

The main method is included in Class Run (in /src) or Run.java (in /bin)

Input commands to create a graph 
> vertex A  
> vertex B  
> vertex C  
> vertex D  
> vertex E  
> edge 2 A B  
> edge 3 B C   
> edge 4 B D  
> edge 8 A C  
> edge 1 D C  
> edge 9 E A  
> weight 6 A C   
> -edge E A   
> -vertex E   
> contents  
vertex A B C D   
edge 2 A B  
edge 6 A C  
edge 4 B D  
edge 3 B C  
edge 1 D C  
> topo  
A B D C    
> path A  
A (0)   
A > B (2)    
A > B > C (5)   
A > B > D (6)   
> path B  
A (unreachable)   
B (0)   
B > C (3)   
B > D (4)   

Though part of the programe uses hash to accelerate, not all functions are using hash.