Java JTree scroll to tree root

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Rectangle;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;

public class Main {
   public static void main(String args[]) {
      final JFrame f = new JFrame("JTree Demo");
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      Container c = f.getContentPane();
      c.setLayout(new FlowLayout());
      DefaultMutableTreeNode root = new DefaultMutableTreeNode("Computer");
      DefaultMutableTreeNode c1 = new DefaultMutableTreeNode("A");
      DefaultMutableTreeNode c2 = new DefaultMutableTreeNode("B");
      DefaultMutableTreeNode c3 = new DefaultMutableTreeNode("C");
      root.add(c1);//from   www  . j  a  v  a 2s.  co m
      root.add(c2);
      root.add(c3);

      c1.add(new DefaultMutableTreeNode("1"));
      c1.add(new DefaultMutableTreeNode("2"));

      c2.add(new DefaultMutableTreeNode("3"));
      c2.add(new DefaultMutableTreeNode("4"));

      c3.add(new DefaultMutableTreeNode("5"));
      c3.add(new DefaultMutableTreeNode("6"));

      JTree t = new JTree(root);
      
      moveHome(t);
      
      c.add(new JScrollPane(t));
      f.pack();
      f.setVisible(true);
   }

   public static void moveHome(JTree tree) {
      showRowCentred(tree, 0);
  }

  private static void showRowCentred(JTree tree, int row) {
      showRowCentred(tree, row, true);
  }

  public static void showRowCentred(JTree tree, int row,
          boolean centerHorizontally) {
      int visible = getVisibleRowCount(tree);
      int top = visible > 0 ? row - (visible - 1) / 2 : row;
      int bottom = visible > 0 ? top + visible - 1 : row;
      showAndSelect(tree, top, bottom, row, centerHorizontally);
  }

  private static int getVisibleRowCount(JTree tree) {
      Rectangle visible = tree.getVisibleRect();
      int count = 0;
      for (int i = 0; i < tree.getRowCount(); i++) {
          Rectangle bounds = tree.getRowBounds(i);
          if (visible.y <= bounds.y
                  && visible.y + visible.height >= bounds.y
                          + bounds.height) {
              count++;
          }
      }
      return count;
  }

  private static void showAndSelect(JTree tree, int top, int bottom,
          int row, boolean centerHorizontally) {
      int size = tree.getRowCount();
      if (size == 0) {
          tree.clearSelection();
          return;
      }
      if (top < 0) {
          top = 0;
      }
      if (bottom >= size) {
          bottom = size - 1;
      }
      Rectangle topBounds = tree.getRowBounds(top);
      Rectangle bottomBounds = tree.getRowBounds(bottom);
      Rectangle bounds;
      if (topBounds == null) {
          bounds = bottomBounds;
      } else if (bottomBounds == null) {
          bounds = topBounds;
      } else {
          bounds = topBounds.union(bottomBounds);
      }
      if (bounds != null) {
          TreePath path = tree.getPathForRow(row);
          if (path != null && path.getParentPath() != null) {
              Rectangle parentBounds = tree.getPathBounds(path
                      .getParentPath());
              if (parentBounds != null) {
                  bounds.x = parentBounds.x;
              }
          }
          if (!centerHorizontally) {
              bounds.x = 0;
              bounds.width = tree.getWidth();
          } else {
              bounds.width = Math.min(bounds.width,
                      tree.getVisibleRect().width);
          }
          tree.scrollRectToVisible(bounds);
      }
      tree.setSelectionRow(row);
  }
}