Update.

src/main/org/insa/algo/strongconnectivity/StronglyConnectedComponentsAlgorithm.java

@@ -0,0 +1,16 @@
+package org.insa.algo.strongconnectivity ;
+
+import org.insa.algo.AbstractAlgorithm;
+
+public abstract class StronglyConnectedComponentsAlgorithm extends AbstractAlgorithm {
+
+	/**
+	 * 
+	 * @param instance
+	 * @param logOutput
+	 */
+	public StronglyConnectedComponentsAlgorithm(StronglyConnectedComponentsInstance instance) {
+		super(instance);
+	}
+
+}

src/main/org/insa/algo/strongconnectivity/StronglyConnectedComponentsInstance.java

@@ -0,0 +1,16 @@
+package org.insa.algo.strongconnectivity;
+
+import org.insa.algo.AbstractInstance;
+import org.insa.graph.Graph;
+
+public class StronglyConnectedComponentsInstance extends AbstractInstance {
+
+	/**
+	 * 
+	 * @param graph
+	 */
+	public StronglyConnectedComponentsInstance(Graph graph) {
+		super(graph);
+	}
+	
+}

src/main/org/insa/algo/strongconnectivity/StronglyConnectedComponentsSolution.java

@@ -0,0 +1,29 @@
+package org.insa.algo.strongconnectivity;
+
+import java.time.Duration;
+import java.util.ArrayList;
+
+import org.insa.algo.AbstractSolution;
+import org.insa.graph.Node;
+
+public class StronglyConnectedComponentsSolution extends AbstractSolution {
+	
+	// Components
+	private ArrayList<ArrayList<Node>> components;
+
+	protected StronglyConnectedComponentsSolution(StronglyConnectedComponentsInstance instance) {
+		super(instance);
+	}
+	
+	protected StronglyConnectedComponentsSolution(StronglyConnectedComponentsInstance instance, 
+					   Duration solvingTime, Status status, ArrayList<ArrayList<Node>> components) {
+		super(instance, solvingTime, status);
+		this.components = components;
+	}
+	
+	/**
+	 * @return Components of the solution, if any.
+	 */
+	public ArrayList<ArrayList<Node>> getComponents() { return components; }
+
+}

src/main/org/insa/algo/strongconnectivity/TarjanAlgorithm.java

@@ -0,0 +1,155 @@
+package org.insa.algo.strongconnectivity;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Stack;
+
+import org.insa.algo.AbstractSolution;
+import org.insa.algo.AbstractSolution.Status;
+import org.insa.graph.Arc;
+import org.insa.graph.Graph;
+import org.insa.graph.Node;
+
+public class TarjanAlgorithm extends StronglyConnectedComponentsAlgorithm {
+	
+	private final static int UNDEFINED = -1;
+
+	// Stack of nodes and flags.
+	private Stack<Node> stack;
+	private boolean[] inStack;
+	
+	// Current index.
+	private int index;
+	
+	// Information of nodes
+	private int[] indexes;
+	private int[] lowlink;	
+	
+	// Array of strongly connected components
+	ArrayList<ArrayList<Node>> components;
+
+	public TarjanAlgorithm(StronglyConnectedComponentsInstance instance) {
+		super(instance);
+	}
+	
+	/**
+	 * Push the given node to the stack.
+	 * 
+	 * @param node
+	 */
+	protected void pushNode(Node node) {
+		stack.push(node);
+		inStack[node.getId()] = true;
+	}
+	
+	/**
+	 * Pop and return a node from the stack.
+	 * 
+	 * @return Node popped from the stack
+	 */
+	protected Node popNode() {
+		Node top = stack.pop();
+		inStack[top.getId()] = false;
+		return top;
+	}
+	
+	/**
+	 * Check if the given node is in the stack.
+	 * 
+	 * @param node
+	 * 
+	 * @return true if the given node is in the stack, false otherwize.
+	 */
+	protected boolean isInStack(Node node) {
+		return inStack[node.getId()];
+	}
+	
+	/**
+	 * Find the strong component containing the given node.
+	 * 
+	 * @param node 
+	 * 
+	 * @return The strong component containing the given node.
+	 */
+	protected void findAndAddStrongComponent(Node v) {
+		Graph graph = getInstance().getGraph();
+		
+		// Update node info, index and push the node.
+		indexes[v.getId()] = index;
+		lowlink[v.getId()] = index;
+		index += 1;
+		pushNode(v);
+		
+		for (Arc a: v.getSuccessors()) {
+			Node w = a.getDestination();
+			if (!hasBeenVisited(w)) {
+				findAndAddStrongComponent(w);
+				lowlink[v.getId()] = Math.min(lowlink[v.getId()], lowlink[w.getId()]);
+			}
+			else if (isInStack(w)) {
+				lowlink[v.getId()] = Math.min(lowlink[v.getId()], indexes[w.getId()]);
+			}
+		}
+		
+		// Compute the component (if any)
+		if (lowlink[v.getId()] == indexes[v.getId()]) {
+			ArrayList<Node> component = new ArrayList<Node>();
+			Node w;
+			do {
+				w = popNode();
+				component.add(w);
+			} while (!w.equals(v));
+			components.add(component);
+			System.out.println("Size of the stack: " + stack.size());
+		}
+				
+	}
+	
+	/**
+	 * Check if the given node has not been visited yet.
+	 * 
+	 * @return true if the node has been visited.
+	 */
+	protected boolean hasBeenVisited(Node node) { 
+		return this.indexes[node.getId()] != UNDEFINED;
+	}
+
+	@Override
+	protected AbstractSolution doRun() {
+		Graph graph = getInstance().getGraph();
+		
+		components = new ArrayList<ArrayList<Node>>();
+		
+		// Starting time...
+		Instant start = Instant.now();
+		
+		// Initialize everything
+		final int nbNodes = graph.getNodes().size();
+		stack = new Stack<Node>();
+		inStack = new boolean[nbNodes];
+		
+		// Current index.
+		index = 0;
+		
+		// Information of nodes
+		indexes = new int[nbNodes];
+		Arrays.fill(indexes, UNDEFINED);
+		lowlink = new int[nbNodes];
+		
+		// Find components
+		for (Node node: graph.getNodes()) {
+			if (!hasBeenVisited(node)) {
+				findAndAddStrongComponent(node);
+			}
+		}
+
+		// Duration...
+		Duration solvingTime = Duration.between(start, Instant.now());
+		
+		return new StronglyConnectedComponentsSolution((StronglyConnectedComponentsInstance)getInstance(),
+					   solvingTime, Status.OPTIMAL, components);
+	}
+
+}