Set Size

Dimension dim = new Dimension(400, 200);
jButton1.setMinimumSize(dim);
jButton1.setPreferredSize(dim);
jButton1.getParent().revalidate();

Reset:
    jButton1.setMinimumSize(null);
    jButton1.setPreferredSize(null);
    jButton1.getParent().revalidate();

Set Foreground Color

jButton1.setForeground(Color.RED);

Reset:
    jButton1.setForeground(null);

Set Background Color

jButton1.setBackground(Color.GREEN);

Reset:
    SynthStyle style = SynthLookAndFeel.getStyle(jButton1, Region.BUTTON);
    SynthContext context = ((SynthButtonUI)jButton1.getUI()).getContext(jButton1);
    jButton1.setBackground((Color)style.get(context, "background"));

Set Border

jButton1.setBorder(new LineBorder(Color.BLUE, 4));

Reset:
    jButton1.setBorder(null);
    jButton1.updateUI();

Hide Border

jButton1.setBorderPainted(false);

Reset:
    jButton1.setBorderPainted(true);

Hide the Focus Border

jButton1.setFocusPainted(false);

Reset:
    jButton1.setFocusPainted(true);

Change Margin

jButton1.setMargin(new Insets(20,20,20,20));

Description:
    Ensures the size of the button is large enough to have this margin around the button text/icon 

Reset:
    jButton1.setMargin(null);

Note:
    Depends on the button border if the margin will resize

Make Opaque

jButton1.setOpaque(true);
jButton1.repaint();

Reset:
    jButton1.setOpaque(false);
    jButton1.repaint();

Make Invisible

jButton1.setContentAreaFilled(false);

Reset:
    jButton1.setContentAreaFilled(true);

Note:
    Will set Opacity to true if setContentAreaFilled is set to true

Change Font

jButton1.setFont(new Font("Courier New", Font.BOLD | Font.ITALIC, 23));

Reset:
    jButton1.setFont(null);

Set Gap between Icon and Text

jButton1.setIconTextGap(40);

Reset:
    jButton1.setIconTextGap(4); //default value