Re: Reading a Random Access File

<http://www.java2s.com/Code/Java/Swing-JFC/AtreemodelusingtheSortTreeModelwithaFilehierarchyasinput.htm>

package computerdatabase;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;

public class Tree extends JFrame
{
  private static final long serialVersionUID = 1L;

  JTree tree;

  public Tree()
  {
    super("Computer Database");
    setSize(300, 400);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    tree = new JTree(initModel());
    getContentPane().add(new JScrollPane(tree));
  }

  public static void main(String args[])
  {
    initDB();
    Tree dbTree = new Tree();
    dbTree.setVisible(true);
  }

  private static void initDB()
  {
    ComputerDatabase dbOut = new ComputerDatabase();
    dbOut.database.put("Classroom 101", new ArrayList<String>());
    dbOut.database.get("Classroom 101").add("#abc101");
    dbOut.database.get("Classroom 101").add("#abc102");
    dbOut.database.get("Classroom 101").add("#abc103");
    dbOut.database.get("Classroom 101").add("#abc104");
    dbOut.database.get("Classroom 101").add("#abc105");
    FileOutputStream fos;
    try
    {
      fos = new FileOutputStream("t.tmp");
      ObjectOutputStream oos = new ObjectOutputStream(fos);
      oos.writeObject(dbOut);
      oos.close();
      fos.close();
    }
    catch (FileNotFoundException e)
    {
      e.printStackTrace();
    }
    catch (IOException e)
    {
      e.printStackTrace();
    }
  }

  private static DefaultTreeModel initModel()
  {
    DefaultTreeModel model = null;
    FileInputStream fis;
    try
    {
      fis = new FileInputStream("t.tmp");
      ObjectInputStream ois = new ObjectInputStream(fis);
      ComputerDatabase dbIn = new ComputerDatabase();
      dbIn = (ComputerDatabase) ois.readObject();
      ois.close();
      fis.close();
      model = new DefaultTreeModel(new DefaultMutableTreeNode(
        "Rooms", true), true);
      for (String rms : dbIn.database.keySet())
      {
        DefaultMutableTreeNode temp =
          new DefaultMutableTreeNode(rms, true);
        ((DefaultMutableTreeNode) model.getRoot()).add(temp);
        for (String cmp : dbIn.database.get(rms))
        {
          ((DefaultMutableTreeNode) model.getChild(model.getRoot(), 0))
          .add(new DefaultMutableTreeNode(cmp, false));
        }
      }
    }
    catch (FileNotFoundException e)
    {
      e.printStackTrace();
    }
    catch (IOException e)
    {
      e.printStackTrace();
    }
    catch (ClassNotFoundException e)
    {
      e.printStackTrace();
    }
    return model;
  }

  static public class ComputerDatabase implements Serializable
  {
    private static final long serialVersionUID = 1L;

    public HashMap<String, ArrayList<String>> database =
      new HashMap<String, ArrayList<String>>();
  }
}