Set Sudoku style border lines created by MatteBorder as cell ruled lines of JTable

• download example.jar
• download src.zip
• repository

Code

static class SudokuCellRenderer extends DefaultTableCellRenderer {
  private final Font font;
  private final Font bold;
  private final Border b0 = BorderFactory.createMatteBorder(
      0, 0, BORDERWIDTH1, BORDERWIDTH1, Color.GRAY);
  private final Border b1 = BorderFactory.createMatteBorder(
      0, 0, BORDERWIDTH2, BORDERWIDTH2, Color.BLACK);
  private final Border b2 = BorderFactory.createCompoundBorder(
      BorderFactory.createMatteBorder(0, 0, BORDERWIDTH2, 0, Color.BLACK),
      BorderFactory.createMatteBorder(0, 0, 0, BORDERWIDTH1, Color.GRAY));
  private final Border b3 = BorderFactory.createCompoundBorder(
      BorderFactory.createMatteBorder(0, 0, 0, BORDERWIDTH2, Color.BLACK),
      BorderFactory.createMatteBorder(0, 0, BORDERWIDTH1, 0, Color.GRAY));
  private final Integer[][] data;
  protected SudokuCellRenderer(Integer[][] src, Font font) {
    super();
    this.font = font;
    this.bold = font.deriveFont(Font.BOLD);
    Integer[][] dest = new Integer[src.length][src[0].length];
    for (int i = 0; i < src.length; i++) {
      System.arraycopy(src[i], 0, dest[i], 0, src[0].length);
    }
    this.data = dest;
  }
  @Override public Component getTableCellRendererComponent(
      JTable table, Object value, boolean isSelected, boolean hasFocus,
      int row, int column) {
    boolean isEditable = data[row][column] == 0;
    super.getTableCellRendererComponent(
        table, value, isEditable && isSelected, hasFocus, row, column);
    if (isEditable && Objects.equals(value, 0)) {
      this.setText(" ");
    }
    setFont(isEditable ? font : bold);
    setHorizontalAlignment(CENTER);
    boolean rf = (row + 1) % 3 == 0;
    boolean cf = (column + 1) % 3 == 0;
    if (rf && cf) {
      setBorder(b1);
    } else if (rf) {
      setBorder(b2);
    } else if (cf) {
      setBorder(b3);
    } else {
      setBorder(b0);
    }
    return this;
  }
}

References

• Set Sudoku style border lines created by MatteBorder as cell ruled lines of JTable(Japanese)