JTreeの選択背景色を変更

class SelectionColorTreeCellRenderer extends DefaultTreeCellRenderer {
  private Color color = null;

  private void setParticularCondition(Object value) {
    if (value instanceof DefaultMutableTreeNode) {
      Object uo = ((DefaultMutableTreeNode) value).getUserObject();
      if (uo instanceof Color) {
        color = (Color) uo;
        return;
      }
    }
    color = null;
  }

  @Override public Component getTreeCellRendererComponent(
      JTree tree, Object value, boolean isSelected, boolean expanded,
      boolean leaf, int row, boolean hasFocus) {
    JComponent c = (JComponent) super.getTreeCellRendererComponent(
        tree, value, isSelected, expanded, leaf, row, hasFocus);
    if (isSelected) {
      setParticularCondition(value);
      c.setForeground(getTextSelectionColor());
      c.setBackground(getBackgroundSelectionColor());
      if (leaf && value.toString().startsWith("a")) {
        c.setOpaque(true);
        c.setBackground(Color.RED);
      } else {
        c.setOpaque(false);
        c.setBackground(getBackgroundSelectionColor());
      }
    } else {
      c.setForeground(getTextNonSelectionColor());
      c.setBackground(getBackgroundNonSelectionColor());
    }
    return c;
  }

  @Override public Color getBackgroundSelectionColor() {
    return color != null ? color : super.getBackgroundSelectionColor();
  }
}