Java Program to Check Cycle in a Graph using Topological Sort

This Java program,to perform the topological Sort on a given graph by the DFS method.The topological sort is performed on a directed acyclic graph.

Here is the source code of the Java program to check for cycle in topological sort. The Java program is successfully compiled and run on a Linux system. The program output is also shown below.

import java.util.InputMismatchException;
import java.util.Scanner;
import java.util.Stack;
 
public class TopoCycle
{
    private Stack<Integer> stack;
 
    public TopoCycle() 
    {
        stack = new Stack<Integer>();
    }
 
    public boolean checkCycle(int adjacency_matrix[][], int source)
    {
        int number_of_nodes = adjacency_matrix.length - 1;
        int[] topological_sort = new int [number_of_nodes + 1];
        int pos = 1;
        int j;
        boolean cycle = false;
 
 
        int visited[] = new int[number_of_nodes + 1];
        int element = source;
        int i = source;
        visited = 1;
        stack.push(source);
 
 
        while (!stack.isEmpty())
        {
            element = stack.peek();
            while (i <= number_of_nodes)
            {
                if (adjacency_matrix[element][i] == 1 && visited[i] == 1)
                {
                    if (stack.contains(i))
                    {
                        System.out.println("The Graph Contains a cycle");
                        cycle = true; 
                        return cycle;
                    }
                }
                if (adjacency_matrix[element][i] == 1 && visited[i] == 0)
                {
                    stack.push(i);
                    visited[i] = 1;
                    element = i;
                    i = 1;
                    continue;
                }
                i++;
            }
            j = stack.pop();	
            topological_sort[pos++] = j;
            i = ++j;
        }
        System.out.println("The Graph does not Contain cycle");
        return cycle;
    }	
 
    public static void main(String...arg)
    {
        int number_no_nodes, source;
        Scanner scanner = null;
        try 
        {
            System.out.println("Enter the number of nodes in the graph");
            scanner = new Scanner(System.in);
            number_no_nodes = scanner.nextInt();
 
            int adjacency_matrix[][] = new int[number_no_nodes + 1][number_no_nodes + 1];
            System.out.println("Enter the adjacency matrix");
	    for (int i = 1; i <= number_no_nodes; i++)
                for (int j = 1; j <= number_no_nodes; j++)
                    adjacency_matrix[i][j] = scanner.nextInt();
 
            System.out.println("Enter the source for the graph");
            source = scanner.nextInt();
 
	    TopoCycle topoCycle = new TopoCycle();
            topoCycle.checkCycle(adjacency_matrix, source);
 
        }catch(InputMismatchException inputMismatch)
        {
            System.out.println("Wrong Input format");
        }
        scanner.close();
    }
}

$javac TopoCycle.java
$java TopoCycle
Enter the number of nodes in the graph
5
Enter the adjacency matrix
0 1 0 1 0
0 0 1 0 0 
0 0 0 0 1
0 1 0 0 1
0 0 0 1 0 
Enter the source for the graph
1
The Graph contains a cycle