Designing graph in JAVA

How to design a Graph in JAVA:-

Vertex:-

package com.problems.graph;

public class Vertex{
  char label;
  boolean visited;
 
  public Vertex(char label){
   this.label=label;
   this.visited=false;
  }
}

Functions of Graphs

public class Graph {

 int maxsize=20;
 Vertex vertex[];
 int matrix[][];
 int vertexcount;
 Stack stackobj;

 public Graph()
 {
  vertex = new Vertex[maxsize];
  matrix=new int[maxsize][maxsize];
  vertexcount=0;
  for(int i=0;i<maxsize;i++)
  {
   for(int j=0;j<maxsize;j++)
   {
    matrix[i][j]=0;
   }
  }
  stackobj=new Stack();   
 }
 
 public void addVertex(char label)
 {
  vertex[vertexcount++]=new Vertex(label);
 }
 public void addEdge(int i,int j)
 {
  matrix[i][j]=1;
  matrix[j][i]=1;
 }
 
 public void displyVertex(int v)
 {
  System.out.println(vertex[v].label);
 }
 

 public int adjVertex(int v)
 {
  for(int i=0;i<maxsize;i++)
  {
   if(matrix[v][i]==1 && vertex[i].visited==false )
    return i;
  }
  return -1;
 }
}