(explain this code please)

class Graph

{

private int V; // No. of vertices

// Array of lists for Adjacency List Representation

private LinkedList adj[];

// Constructor

Graph(int v) {

V = v;

adj = new LinkedList[v];

for (int i=0; i

adj[i] = new LinkedList();

} //initialize the list with 0 values.

}

// Function to add an edge into the graph

void addEdge(int v, int w) { adj[v].add(w); }

// A recursive function used by topologicalSort

void topologicalSortUtil(int v, boolean visited[], Stack stack) {

// Mark the current node as visited.

visited[v] = true;

Integer i;

// Recur for all the vertices adjacent to this vertex

Iterator it = adj[v].iterator();

while (it.hasNext()) {

i = it.next();

if (!visited[i]) { topologicalSortUtil(i, visited, stack); }

} // Push current vertex to stack which stores result //push the element in stack after recursion ends.

stack.push(new Integer(v)); } // The function to do Topological Sort. It uses recursive //topological sort function call from here.

void topologicalSort() {

Stack stack = new Stack();

boolean visited[] = new boolean[V];

for (int i = 0; i < V; i++)

visited[i] = false;

// Call the recursive helper

// function to store

// Topological Sort starting

// from all vertices one by one

for (int i = 0; i < V; i++)

if (visited[i] == false)

topologicalSortUtil(i, visited, stack);

// Print contents of stack

while (stack.empty() == false)

System.out.print(stack.pop() + " ");

}

}