线程“ AWT-EventQueue-0”中的java异常java.lang.IllegalArgumentException

Question

I was trying my first code in java swing and got many errors. my code is:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class Swinging extends JFrame
{
    JTextField ans;
    int count =0;
    static final long serialVersionUID = 1L; 
    Swinging()
    {
         Container cp= getContentPane();
         cp.setLayout(new FlowLayout());

         cp.add(new JLabel("value",7));

         ans=new JTextField("0",10);
         cp.add(ans);

         JButton inc= new JButton("increment");
         cp.add(inc);

         inc.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
                ++count;
                ans.setText(count+"");
            }
         });

        setSize(200,200);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     }
 }


public class Usingswing {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

             public void run() {
                new Swinging(); // Let the constructor do the job
             }
          });

    }

}

and the errors are as follows:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: horizontalAlignment
at javax.swing.JLabel.checkHorizontalKey(Unknown Source)
at javax.swing.JLabel.setHorizontalAlignment(Unknown Source)
at javax.swing.JLabel.<init>(Unknown Source)
at javax.swing.JLabel.<init>(Unknown Source)
at hopeso.Swinging.<init>(Usingswing.java:16)
at hopeso.Usingswing$1.run(Usingswing.java:45)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

i tried solving my problem using the questions posted by other people but it didn't workout. please help.

Answer 1

The error occurs because of the following line:

cp.add(new JLabel("value",7));

You're using JLabel 's constructor that receives the text and the horizontal alignment. The alignment is an int , but it has to be one of the following constants, otherwise it will throw the IllegalArgumentException :

• LEFT (2)
• CENTER (0)
• RIGHT (4)
• LEADING (10)
• TRAILING (11)

These constants are defined in SwingConstants , so you can just write something like this:

cp.add(new JLabel("value", SwingConstants.CENTER));