The Graph class below represents an UNDIRECTED graph. Complete the constructor and methods.

class Graph $\{$

Map$>$ adjacencies;

public Graph$()\{$

$\}$

public void addVertex$($V v$)\{$

$//$ ensures that vertex v is in the graph

$\}$

public void addEdge$($V v$1,$ V v$2)\{$

$//$ adds an edge between vertices v$1$ and v$2$

$//$ throws an IllegalArgumentException if

$//$ either v$1$ or v$2$ are not in the graph

$\}$

public boolean hasEdge$($V v$1,$ V v$2)\{$

$//$ returns true if there is an edge between v$1$ and v$2$

$//$ and false otherwise. Returns false

$//$ in all other cases $($this doesn't throw an exception$)$

$\}$

public void removeEdge$($V v$1,$ V v$2)\{$

$//$ ensures that the graph does not

$//$ have an edge between vertices v$1$ and v$2$

$\}$

$\}$