Create an Adjacency matrix Graph and perform Add and Remove operation

import java.util.ArrayList;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.Stack;

/**
 * Implementation of a directed unweighted Graph using Adjacency Matrix
 * 
 * Complexity: addEdge, removeEdge, hasEdge O(1) / outEdges, inEdges O(n) /
 * Space O(n^2)
 */
public class AdjMatrixGraph {
 int size;
 private boolean[][] matrix;
 public static final byte WHITE = 1;
 public static final byte GREY = 2;

 public AdjMatrixGraph(int size) {
  this.size = size;
  this.matrix = new boolean[size][size];
 }

 public void addEdge(int nodeA, int nodeB) {
  matrix[nodeA][nodeB] = true;
 }

 public void removeEdge(int nodeA, int nodeB) {
  matrix[nodeA][nodeB] = false;
 }

 public boolean hasEdge(int nodeA, int nodeB) {
  return matrix[nodeA][nodeB];
 }

 public List<Integer> outEdges(int i) {
  List<Integer> edges = new ArrayList<Integer>();
  for (int j = 0; j < size; j++) {
   if (matrix[i][j]) {
    edges.add(j);
   }
  }
  return edges;
 }

 public List<Integer> inEdges(int i) {
  List<Integer> edges = new ArrayList<Integer>();
  for (int j = 0; j < size; j++) {
   if (matrix[j][i]) {
    edges.add(j);
   }
  }
  return edges;
 }

 public int nVertices() {
  return size;
 }

 public void breadthFirstSearch(int root) {
  boolean[] seen = new boolean[nVertices()];
  Queue<Integer> q = new LinkedList<Integer>();
  q.add(root);
  seen[root] = true;
  while (!q.isEmpty()) {
   int i = q.remove();
   for (Integer j : outEdges(i)) {
    if (!seen[j]) {
     q.add(j);
     seen[j] = true;
    }
   }
  }
 }

 public void depthFirstSearch(int r) {
  byte[] c = new byte[nVertices()];
  Stack<Integer> s = new Stack<Integer>();
  s.push(r);
  while (!s.isEmpty()) {
   int i = s.pop();
   if (c[i] == WHITE) {
    c[i] = GREY;
    for (int j : outEdges(i))
     s.push(j);
   }
  }
 }

 public static void main(String[] args) {
  AdjMatrixGraph graph = new AdjMatrixGraph(10);

  graph.addEdge(1, 3);
  graph.addEdge(2, 4);
  graph.addEdge(6, 8);
  graph.addEdge(3, 2);

  System.out.println("Edge from 6 to 8 is : " + graph.hasEdge(6, 8));
  System.out.println("Edge from 2 to 4 is : " + graph.hasEdge(2, 4));
  System.out.println("Edge from 3 to 2 is : " + graph.hasEdge(3, 2));
  System.out.println("Edge from 1 to 3 is : " + graph.hasEdge(1, 3));

  graph.removeEdge(6, 8);
  System.out.println("Edge from 6 to 8 is : " + graph.hasEdge(6, 8));

 }
}

Output of this Program:

Edge from 6 to 8 is : true
Edge from 2 to 4 is : true
Edge from 3 to 2 is : true
Edge from 1 to 3 is : true
Edge from 6 to 8 is : false

Try this by Yourself : http://ideone.com/ZZm7rW