I'm a newer in Java and now about to use adjacency matrix(2D array) to implement a graph, but encountered some problems, pls help me,thanks. following are partly codes.

// following codes create a empty graph

public AdjMatrix() {

private boolean[][] adjacencymatrix; /*Define a 2D array to store adjacency matrix*/

private int vertices_numb; /*Number of vertices in the graph */

T[] vertices; /*To store the values of vertices*/

vertices_numb=0 /*set the graph to empty*/

} // end of AdjMatrix()

//Following code is for adding a vertex.

public void addVertex(T vertLabel) {

if (vertices_numb == 0) //If the graph is empty, print related information and assign value 0 to adjacency matrix[0][0]

System.out.println("Graph is empty!");

adjacencymatrix[0][0]=0;

vertices[0]=vertLabel; //To save the vertex

vertices_numb=vertices_numb+1; //to count the number of vertex

else

for(int i=0;i<=vertices_numb;i++) {

vertices[vertices_numb]=vertLabel;

adjacencymatrix[i][vertices_num]= how does program know they are connected between 2 nodes?

vertices_numb=vertices_numb+1;

}

} // end of addVertex()

My problems are:

1) How does program know if they are connected between two nodes?

2) When adding a vertex, do we need to consider the connection between this one with the nodes exist?

Many thanks.