Detect Cycle in a Directed Graph using DFS

DFScycle.java

import java.util.*;
import java.io.*;

public class Graph{
    int V;
    LinkedList<Integer> list[];

    Graph(int V){
        this.V=V;
        list = new LinkedList[V];
        for(int i=0;i<V;i++){
            list[i]=new LinkedList<Integer>();
        }
    }
  
    public void addEdge(int x, int y)
    {
        list[x].addFirst(y);
    }
    
    public boolean isCycle(){
        
        boolean visited[] = new boolean[V];
        boolean rec[]= new boolean[V];

        //DFS
        for(int i=0;i<V;i++)
        {
            if(isCycleUtil(i,visited,rec))
                return true;
        }
        return false;
    }
    
    public boolean isCycleUtil(int v, boolean visited[],boolean rec[]){
     
      visited[v]=true;
      rec[v]=true;
        
        // recursive call to all the adjcent vertices;
        
        for(int i=0;i<list[v].size();i++)
        {
            //if not visited already
            int adjv = list[v].get(i);
            if(!visited[adjv] && isCycleUtil(adjv , visited, rec))
                return true;
            else if(rec[adjv])
                return true;
        }
        rec[v]=false;
        return false;
        
}
    public void printgraph(){
        for(int i=0;i<V;i++)
        {
            LinkedList<Integer> nlist = list[i];
            if(nlist.isEmpty()==false){
                System.out.print("source = " + i + " => ");
                for(int j=0;j<nlist.size();j++)
                {
                    System.out.print(" " + nlist.get(j));
                }
            }
            System.out.println("");
        }
    }
    
    
    public static void main(String [] args)
    {
        Graph g = new Graph(5);
        g.addEdge(0,1);
        g.addEdge(0,2);
        g.addEdge(1,3);
        g.addEdge(3,1);
        g.addEdge(3,4);
        g.addEdge(4,4);
        g.addEdge(4,0);
        g.printgraph();
        boolean result = g.isCycle();
        System.out.println("is cycle present "+result);
        
    }
}
/*      SOLUTION        */
/*
source = 0 =>  2 1
source = 1 =>  3

source = 3 =>  4 1
source = 4 =>  0 4
is cycle present true



*/