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How do I remove this line in JComboBox

So, this problem I am having is ruining the looks of the game I'm making. I don't know what it is, but I don't know how to remove it.
I was wondering if maybe there was a component I didn't color so I ran this, and it still didn't change anything.
for ( int i = 0; i < comboBox.getComponentCount(); i++)
{
if ( comboBox.getComponent(i) instanceof JComponent)
{
( (JComponent) comboBox.getComponent( i ) ).setBorder( new EmptyBorder( 0, 0, 0, 0) );
( (JComponent) comboBox.getComponent( i ) ).setBackground( background );
( (JComponent) comboBox.getComponent( i ) ).setForeground( foreground );
}
if ( comboBox.getComponent(i) instanceof AbstractButton)
{
( (AbstractButton) comboBox.getComponent( i ) ).setBorderPainted( false );
( (AbstractButton) comboBox.getComponent( i ) ).setBackground( background );
( (AbstractButton) comboBox.getComponent( i ) ).setForeground( foreground);
}
}
If anyone has any ideas that would be helpful.

how can i use setPreferredSize in java?

I have a problem: I want to create a small game, I have to make a window like the following:
When I tried to change the font size of "Fun With Words", it wasn't changed ...
What should I do?
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JComponent;
public class GameWords extends JFrame
{
private static int W = 800 ;
private static int H = 600 ;
public GameWords ()
{
setTitle ( " Word Order Game " ) ;
setSize ( H , W ) ;
setLayout ( new FlowLayout() ) ;
setDefaultCloseOperation ( EXIT_ON_CLOSE ) ;
createContent () ;
setVisible ( true ) ;
}
public void createContent ()
{
JLabel heading = new JLabel (" Fun With Words ") ;
heading.setFont ( heading.getFont().deriveFont ( 26f ) );
heading.setPreferredSize ( new Dimension ( H , 4 * W ) ) ;
JLabel h1 = new JLabel ( " Hey Kids! Want to prictice your typing and word-ordering Skills ? \n" ) ;
add ( heading ) ;
add ( h1 ) ;
}
public static void main(String[] args)
{
new GameWords () ;
}
}

The short answer is don't, the API is quite capable of calculating the desired size it self.
The longer answers is, don't use setSize, use pack instead, which uses the containers preferred size to calculate the size of the window
public GameWords ()
{
setTitle ( " Word Order Game " ) ;
setLayout ( new FlowLayout() ) ;
setDefaultCloseOperation ( EXIT_ON_CLOSE ) ;
createContent () ;
pack();
setVisible ( true ) ;
}
public void createContent ()
{
JLabel heading = new JLabel (" Fun With Words ") ;
heading.setFont ( heading.getFont().deriveFont ( 26f ) );
JLabel h1 = new JLabel ( " Hey Kids! Want to prictice your typing and word-ordering Skills ? \n" ) ;
add ( heading ) ;
add ( h1 ) ;
}
As a general recommendation, you shouldn't extend directly from a JFrame, you're not adding any new functionality to the class and you're locking yourself into a single use case. As a general recommendation, you should start by extending from JPanel and then add this to whatever container you want to use

JPopupMenu Menu Items and Components

I have a popup menu which contains a JMenuItem with an icon (I) and a JList. See the diagram below.
------------------------
| I | Clear |
|----------------------|
| | List |^|
| | Item A | |
| | Item B | |
| | Item C | |
| | |v|
------------------------
When I initially created the popup, the list was aligned to the left hand side and did not take into account the icon offset.
I was able to find a way to move the list using the sun.swing.SwingUtilities2.BASICMENUITEMUI_MAX_TEXT_OFFSET client property.
// Move the items out of the gutter (Run inside of the show(Component, int, int) method)
final Integer gutter = (Integer) getClientProperty(SwingUtilities2.BASICMENUITEMUI_MAX_TEXT_OFFSET);
panelList.removeAll();
panelList.add(Box.createHorizontalStrut(gutter));
panelList.add(scrollList);
However, I am unable to use that constant in production code (due to it being in the sun package).
How can I retrieve the max text/icon offset without relying upon Java's internals?

One common solution for this is to add an empty Icon for each menu item that is the same size as the Icon for the menu.
You might be able to use the concepts from the code below which uses:
SwingUtilities.layoutCompoundLabel(...);
Basically it get the layout information of the label to determine where the text and icon are actually painted relative to the entire label. If you know that information you should then have your offset.
This example paints grid lines only over the Icon in the label:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class LabelLayout extends JLabel
{
#Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics grid = g.create();
grid.setColor( Color.ORANGE );
Rectangle viewR = new Rectangle();
viewR.width = getSize().width;
viewR.height = getSize().height;
Rectangle iconR = new Rectangle();
Rectangle textR = new Rectangle();
String clippedText = SwingUtilities.layoutCompoundLabel
(
this,
grid.getFontMetrics(),
getText(),
getIcon(),
getVerticalAlignment(),
getHorizontalAlignment(),
getVerticalTextPosition(),
getHorizontalTextPosition(),
viewR,
iconR,
textR,
getIconTextGap()
);
int gridSize = 10;
int start = iconR.x;
int end = iconR.x + iconR.width;
System.out.println( iconR );
for (int i = start; i < end; i += gridSize)
{
grid.drawLine(i, iconR.y, i, iconR.y + iconR.height);
}
grid.dispose();
// g.setColor( getForeground() );
// g.drawString(display, textR.x, textR.y + fm.getHeight());
// System.out.println(iconR + " : " + textR);
}
private static void createAndShowGUI()
{
LabelLayout label = new LabelLayout();
label.setBorder( new LineBorder(Color.RED) );
label.setText( "Some Text" );
label.setIcon( new ImageIcon( "DukeWaveRed.gif" ) );
label.setVerticalAlignment( JLabel.CENTER );
label.setHorizontalAlignment( JLabel.CENTER );
// label.setVerticalTextPosition( JLabel.BOTTOM );
label.setVerticalTextPosition( JLabel.TOP );
label.setHorizontalTextPosition( JLabel.CENTER );
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( label );
frame.setLocationByPlatform( true );
frame.pack();
frame.setSize(300, 200);
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}
I think a JMenu would use the same layout.

How to account for input errors in calculator program?

I'm writing a calculator program for my java class. I want to account for errors like
User decides to divide by 0. I want the calculator to be able to acknowledge this error and display ERROR.
The user enters 6+7+ and then hits the equal button.
I want, once again, for the calculator to acknowledge that there is an error. I was hoping I could get some hints as to how to go about this. Thanks!
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Calculator
{
JFrame window;
// stuff for top panel
JPanel topPanel;
JTextField expr,result;
JButton equals;
// stuff for bottom panel
JPanel bottomPanel,digitsPanel,opsPanel;
JButton[] digits,ops;
JButton clear, clearEntry;
Container content;
Listener listener;
String[] oplabels = { "+", "-", "/", "*" };
public Calculator()
{
listener = new Listener(); // our Listener class implements ActionListener
window= new JFrame("GUI Calc");
content=window.getContentPane();
content.setLayout( new GridLayout(2,1) );
topPanel=new JPanel();
topPanel.setLayout( new GridLayout(1,3) );
// TOP PANEL WORK
expr = new JTextField( );
equals = new JButton("=");
equals.addActionListener( listener );
result = new JTextField( );
topPanel.add( expr );
topPanel.add( equals );
topPanel.add( result );
// BOTTOM PANEL WORK
bottomPanel = new JPanel();
bottomPanel.setLayout( new GridLayout(1,2) );
digitsPanel = new JPanel();
digitsPanel.setLayout( new GridLayout(4,3) );
opsPanel = new JPanel();
opsPanel.setLayout( new GridLayout(4,1) );
digits = new JButton[12];
ops = new JButton[4];
for (int i=0 ; i<10 ; i++)
{
digits[i] = new JButton( i+"" );
digits[i].addActionListener(listener);
digitsPanel.add( digits[i] );
}
clear = new JButton( "C" );
clearEntry = new JButton( "CE" );
clear.addActionListener(listener);
clearEntry.addActionListener(listener);
digitsPanel.add( clear );
digitsPanel.add( clearEntry);
for (int i=0 ; i<4 ; i++)
{
ops[i] = new JButton( oplabels[i] ) ;
ops[i].addActionListener(listener);
opsPanel.add( ops[i] );
}
bottomPanel.add( digitsPanel );
bottomPanel.add( opsPanel );
content.add( topPanel);
content.add( bottomPanel);
window.setVisible(true);
}
class Listener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
Component clicked = (Component) e.getSource();
if ( clicked == equals )
{
result.setText( evaluate( expr.getText() ) );
return;
}
for ( int i=0 ; i<10 ; i++)
{
if ( clicked == digits[i] )
{
expr.setText( expr.getText() + i );
return;
}
}
if ( clicked == clear )
{
expr.setText("0");
return;
// do something
}
/* if (clicked == clearEntry)
{
expr.setText(expr.getDigits[i]);
}
for (int i=0; i < 10; i++)
{
if (clicked == digits[i])
{
int lastValue = clicked;
if(clicked == clearEntry)
{
expr.setText(expr.getText()-clicked);
return;
}
}
} */
for ( int i=0 ; i<4 ; i++ )
{
if(clicked == digits[i])
{
expr.setText(expr.getText() + oplabels[i]);
return;
}
// tack on that operator to the expr string
}
}
String evaluate( String exp )
{
return "NOT WRITTEN YET";
}
}
public static void main(String [] args)
{
new Calculator();
}
}
I'm still working on it. Especially where I'm trying to figure out the clearEntry button so I have put that section as a comment because its still a work in progress.

You can try this:
add a new class(Calculator) member:
Component last_clicked;
Inside Constructor:
last_clicked=null;
Before every return statement of actionPerformed, you can add this:
last_clicked=clicked;
Now, in actionPerformed method, when checking value of clicked, you can do this:
When clicked is '0' & last_clicked is '/', you can display error 1.
When clicked is 'equals' & last_clicked is an operator, you can display error 2.

didn't understand action listner of radio buttons

when i click adjacent two radio button then a line drawn between these button i put conditions in my code that line only will draw when two horizontal or vertical radio button selected else it show a error message ........... it works for me but if i click randomly two radio button it will throw an exception which i cant understand please give some discription about answer because i am beginner too............ and what is this means it shows when i compile prog..........Note: C:\Users\MUHAMMAD Umair\Desktop\ComponentLinkerTest.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.HashMap;
import java.util.Map;
import java.util.*;
/**
* #see http://stackoverflow.com/a/12389479/909085
*/
public class ComponentLinkerTest extends JComponent
{
// private Map<JComponent, JComponent> linked;
Map<JComponent, java.util.List<JComponent> > linked;// = new HashMap<>();
int n=1;
public ComponentLinkerTest ()
{
super ();
linked = new HashMap ();
}
static JRadioButton[] button = new JRadioButton[25];
public void gui()
{
setupLookAndFeel ();
JFrame frame = new JFrame ();
linker = new ComponentLinkerTest ();
frame.setGlassPane ( linker );
linker.setVisible ( true );
JPanel content = new JPanel ();
content.setLayout ( new GridLayout ( 5, 5, 5, 5 ) );
content.setBorder ( BorderFactory.createEmptyBorder ( 5, 5, 5, 5 ) );
frame.add ( content );
int i;
for (i = 0; i < 25; i++ )
{
// final JButton button = new JButton ( "Button" + i );
button[i] = new JRadioButton();
// panel.add(fontButtons[i]);
button[i].addActionListener ( new ActionListener ()
{
public void actionPerformed ( ActionEvent e )
{
link ((JRadioButton) e.getSource() );
}
} );
content.add ( button [i]);
}
frame.setDefaultCloseOperation ( JFrame.EXIT_ON_CLOSE );
frame.pack ();
frame.setLocationRelativeTo ( null );
frame.setVisible ( true );
}
/*public void link ( JComponent c1, JComponent c2 )
{
linked.put ( c1, c2 );
repaint ();
}*/
public void link ( JComponent c1, JComponent c2 )
{
if(linked.containsKey(c1)){
linked.get(c1).add(c2);
}else{
java.util.List<JComponent> list = new LinkedList<>();
list.add(c2);
linked.put ( c1, list );
}
repaint ();
}
/* protected void paintComponent ( Graphics g )
{
Graphics2D g2d = ( Graphics2D ) g;
g2d.setRenderingHint ( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON );
g2d.setPaint ( Color.BLACK );
for ( JComponent c1 : linked.keySet () )
{
Point p1 = getRectCenter ( getBoundsInWindow ( c1 ) );
Point p2 = getRectCenter ( getBoundsInWindow ( linked.get ( c1 ) ) );
/* Stroke stroke = new BasicStroke(8//,
/*BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL, 0,
new float[] { 12, 12 }, 0);
g2d.setStroke(stroke);
g2d.setColor(Color.RED);
g2d.drawLine ( p1.x, p1.y, p2.x, p2.y );
}
}*/
#Override
protected void paintComponent ( Graphics g )
{
super.paintComponent(g);
Graphics2D g2d = ( Graphics2D ) g;
g2d.setRenderingHint ( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON );
g2d.setPaint ( Color.BLACK );
for ( JComponent c1 : linked.keySet () )
{
for(JComponent c2 : linked.get(c1)){
Point p1 = getRectCenter ( getBoundsInWindow ( c1 ) );
Point p2 = getRectCenter ( getBoundsInWindow ( c2 ) );
/* Stroke stroke = new BasicStroke(8//,
/*BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL, 0,
new float[] { 12, 12 }, 0);
g2d.setStroke(stroke);*/
if(n==1)
{
g2d.setColor(Color.RED);
n=2;
}
else
{
g2d.setColor(Color.BLUE);
n=1;
}
g2d.drawLine ( p1.x, p1.y, p2.x, p2.y );
}
}
}
private Point getRectCenter ( Rectangle rect )
{
return new Point ( rect.x + rect.width / 2, rect.y + rect.height / 2 );
}
private Rectangle getBoundsInWindow ( Component component )
{
return getRelativeBounds ( component, getRootPaneAncestor ( component ) );
}
private Rectangle getRelativeBounds ( Component component, Component relativeTo )
{
return new Rectangle ( getRelativeLocation ( component, relativeTo ),
component.getSize () );
}
private Point getRelativeLocation ( Component component, Component relativeTo )
{
Point los = component.getLocationOnScreen ();
Point rt = relativeTo.getLocationOnScreen ();
return new Point ( los.x - rt.x, los.y - rt.y );
}
private JRootPane getRootPaneAncestor ( Component c )
{
for ( Container p = c.getParent (); p != null; p = p.getParent () )
{
if ( p instanceof JRootPane )
{
return ( JRootPane ) p;
}
}
return null;
}
public boolean contains ( int x, int y )
{
return false;
}
private static ComponentLinkerTest linker;
public static void main ( String[] args )
{
ComponentLinkerTest ct = new ComponentLinkerTest();
ct.gui();
}
private static JRadioButton last = null;
private static void link ( JRadioButton buton )
{
int a=0;
int i;
if ( last == null )
{
last = buton;
System.out.println(last.getX());
}
else
{
for( i=0 ;i<25 ;i++)
{
if(buton == button[i])
{
if(button[i-1] == last || button[i+1]==last || button[i-5] == last || button[i+5]==last)
{
System.out.println("in cond");
linker.link ( last, buton );
buton.setSelected(false);
last.setSelected(false);
last = null;
}
else
{
System.out.println("out cond");
buton.setSelected(false);
last.setSelected(false);
last = null;
JOptionPane.showMessageDialog(null,"Wrong position clicked ");
}
break;
}
else
{
System.out.println("button not found");
}
}
}
}
private static void setupLookAndFeel ()
{
try
{
UIManager.setLookAndFeel ( UIManager.getSystemLookAndFeelClassName () );
}
catch ( ClassNotFoundException e )
{
e.printStackTrace ();
}
catch ( InstantiationException e )
{
e.printStackTrace ();
}
catch ( IllegalAccessException e )
{
e.printStackTrace ();
}
catch ( UnsupportedLookAndFeelException e )
{
e.printStackTrace ();
}
}
}

You do no range checking...
This is going to cause an exception if you the last button is the on the last line, or the second button is one the first row
if (button[i - 1] == last || button[i + 1] == last || button[i - 5] == last || button[i + 5] == last)
You need to modify your checks to ensure that they don't extend below (0) or beyond (button.length - 1)...
if ((i > 0 && button[i - 1] == last) ||
(i < (button.length - 1) && button[i + 1] == last) ||
(i > 5 && button[i - 5] == last) ||
(i < (button.length - 1) && button[i - 5] == last)) {
Updated with alternative
Okay, that if statement was doing my head...so I took a different tact...
Basically, instead, I found the index of each button and calculated the distance that each button was from each other, they could only be 1 or 5 indices apart...
int lastIndex = indexOf(last);
int currentIndex = indexOf(buton);
int diff = Math.max(lastIndex, currentIndex) - Math.min(lastIndex, currentIndex);
if (diff == 1 || diff == 5) {
System.out.println("in cond");
linker.link(last, buton);
buton.setSelected(false);
last.setSelected(false);
last = null;
} else {
System.out.println("out cond");
buton.setSelected(false);
last.setSelected(false);
last = null;
JOptionPane.showMessageDialog(null, "Wrong position clicked ");
}
And the indexOf method...
protected static int indexOf(JRadioButton btn) {
int index = -1;
for (int value = 0; value < button.length; value++) {
if (button[value].equals(btn)) {
index = value;
break;
}
}
return index;
}
As a side note, I'd also beware of over using static. This suggest a bad design