本题的功能是用按钮来控制文本框中文本的颜色。窗口中有两个带有文字标题的面板“Sample text”和“Text color control”，窗口的底部还有一个复选按钮“Disable changes”。在“Sample text”面板中有一个带有字符串的文本框，而在“Text color control”面板中有三个按钮“Black”、“Red”和“Green”，并且每个按钮上都有一个对应颜色的圆。单击任意按钮，文本框的文本变成对应的颜色，如果选中“Disable changes”复选框，则三个颜色按钮变为不可用，如果取消选中复选框，则三个按钮变为可用。
import javax. swing. * ;
import java. awt. * ;
import java. awt. event. * ;
public class java3 extends JFrame
private JPanel upper, middle, lower;
private JTextField text;
private JButton black, red, green;
private JCheckBox disable;
public java3 (String titleText)
super (titleText);
addWindowListener (new WindowAdapter()
public void
windowClosing (WindowEvent e)
System. exit(0);

);
upper=new JPanel();
upper. setBorder (BorderFactory. createTitledBorder("Sample text"));
Upper. setlayout(new BorderLayout());
text=new JTextField ("Change the color of this text");
upper. add (text, BorderLayout. CENTER);
middle=new JPanel();
middle, setBorder (BorderFactory. createTitledBorder("Text color control"));
middle, setLayout (new FlowLayout (FlowLayout. CENTER));
black=new JButton (" Black", new ColorIcon (Color. black));
black, addActionListener (new ButtonListener (Color. black));
middle, add (black);
red=new JButton( "Red", new ColorIcon (Color. red));
red. addActionListener (new ButtonListener (Color. red));
middle, add (red);
green=new JButton ("Green", new ColorIcon (Color. green));
green, addActionListener (new ButtonListener (Color. green));
middle, add (green);
lower=new JPanel();
lower, setLayout (new FlowLayout (FlowLayout. RIGHT));
disable=new JCheckBox ("Disable changes");
disable, addItemListener (new ItemListener()
public void itemStateChanged (hemEvent e)
boolean enabled
=(e. getStateChange()
=ItemEvent. DESELECTED);
black, setEnabled (enabled);
red. setEnabled (enabled);
green. setEnabled (enabled);


);
lower, add (disable);
Container cp = getContentPane();
cp. add (upper, BorderLayout. NORTH);
cp. add (middle, BorderLayout. CENTER);
cp. add (lower, BorderLayout. SOUTH);
pack ();
setVisible (true);

class ButtonListener extends ActionListener
private Color c;
public ButtonListener (Color c)
this. c=c;

public void actionPerformed (ActionEvent e)
text. setForeground (c);


class Colorlcon implements Icon
private Color c;
private static final int DIAMETER=10;
public Colorlcon (Color c)
c=c;

public void paintlcon (Component cp, Graphics g, int x, int y)
g. setColor (c);
g. fillOvaI (x, y, DIAMETER, DIAMETER);
g. setColor (Color. black);
g. drawOval (x, y, DIAMETER, DIAMETER);

public int getIconHeight()
return DIAMETER;

public int getIconWidth()
return DIAMETER;


public static void main (String[]args)
new java3 ("java3");