GraphDraw.java

import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class GraphDraw extends JFrame {
     int width;
     int height;
     
     ArrayList<Node> nodes;
     ArrayList<edge> edges;
     
     public GraphDraw() { //Constructor
          this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          nodes = new ArrayList<Node>();
          edges = new ArrayList<edge>();
          width = 30;
          height = 30;
     }
     
     public GraphDraw(String name) { //Construct with label
          this.setTitle(name);
          this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          nodes = new ArrayList<Node>();
          edges = new ArrayList<edge>();
          width = 30;
          height = 30;
     }
     
     class Node {
          int x, y;
          String name;
          
          public Node(String myName, int myX, int myY) {
               x = myX;
               y = myY;
               name = myName;
          }
     }
     
     class edge {
          int i,j;
          
          public edge(int ii, int jj) {
               i = ii;
               j = jj;     
          }
     }
     
     public void addNode(String name, int x, int y) { 
          //add a node at pixel (x,y)
          nodes.add(new Node(name,x,y));
          this.repaint();
     }
     public void addEdge(int i, int j) {
          //add an edge between nodes i and j
          edges.add(new edge(i,j));
          this.repaint();
     }
     
     public void paint(Graphics g) { // draw the nodes and edges
          FontMetrics f = g.getFontMetrics();
          int nodeHeight = Math.max(height, f.getHeight());
          
          g.setColor(Color.black);
          for (edge e : edges) {
               g.drawLine(nodes.get(e.i).x, nodes.get(e.i).y,
                          nodes.get(e.j).x, nodes.get(e.j).y);
          }
          
          for (Node n : nodes) {
               int nodeWidth = Math.max(width, f.stringWidth(n.name)+width/2);
               g.setColor(Color.white);
               g.fillOval(n.x-nodeWidth/2, n.y-nodeHeight/2, 
                          nodeWidth, nodeHeight);
               g.setColor(Color.black);
               g.drawOval(n.x-nodeWidth/2, n.y-nodeHeight/2, 
                          nodeWidth, nodeHeight);
               
               g.drawString(n.name, n.x-f.stringWidth(n.name)/2,
                            n.y+f.getHeight()/2);
          }
     }
}