title: int field validation in swing for user registration form
body: <p>Swing work
    I am having difficulties doing a simple validation of a text field that has as a value - an int variable.  I need the following:</p>
  
  <ul>
  <li>permit only digits</li>
  <li>don't allow a value of 0 or bellow</li>
  <li>It has to be mandatory to fill .</li>
  </ul>
  
  
  
  <pre><code>private void btnsaveActionPerformed(java.awt.event.ActionEvent evt) 
  
  {                                         
          // TODO add your handling code here:
  
     User controller=new User(
  
     new Integer(textuid.getText().trim()),textname.getText(),
     textpassword.getText(),textrepassword.getText());
     controller.saveUser(db.getCon());
  
     // int a= new Integer(textuid.getText().trim());
     System.out.print(controller.getUid());
  
     if(Integer.parseInt(textuid.getText()) &lt;=0){
        JOptionPane.showMessageDialog( textuid, "Must enter a value greater than zero"); }
     if(textuid.getText().equals("s")){
             JOptionPane.showMessageDialog( textuid, "Must enter a value greater than zero"); }
  //        if(textname.getText().equals(""))
  //            {
  //           JOptionPane.showMessageDialog( textname, "Name not empty"); 
  //        }
  //           if(textpassword.getText().equals("")){
  //           JOptionPane.showMessageDialog( textname, "Password not empty"); 
  //        }
  //           if(textrepassword.getText().equals("")){
  //           JOptionPane.showMessageDialog( textname, "Password not empty"); 
  //        }
      }          
  </code></pre>
  
  <p>show error message</p>
  
  <pre><code>Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: ""
  at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
  at java.lang.Integer.parseInt(Integer.java:470)
  at java.lang.Integer.&lt;init&gt;(Integer.java:660)
  at com.smart.ui.UserForm.btnsaveActionPerformed(UserForm.java:149)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
  at java.awt.Component.processMouseEvent(Component.java:6267)
  at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
  at java.awt.Component.processEvent(Component.java:6032)
  at java.awt.Container.processEvent(Container.java:2041)
  at java.awt.Component.dispatchEventImpl(Component.java:4630)
  at java.awt.Container.dispatchEventImpl(Container.java:2099)
  at java.awt.Component.dispatchEvent(Component.java:4460)
  at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
  at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)
  at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
  at java.awt.Container.dispatchEventImpl(Container.java:2085)
  at java.awt.Window.dispatchEventImpl(Window.java:2478)
  at java.awt.Component.dispatchEvent(Component.java:4460)
  at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
  at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
  at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
  at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
  at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
  </code></pre>
  
  <p>I can't solve this. please help. it's my first post</p>