title: Swing NullPointer
body: <p>Hi i'm trying to add actionlistener that would take an input from the user and change the color of the background, but i'm getting this error... would you please be specific and give an answer for a beginner... thanks <code>enter code here</code></p>
  
  <pre><code>package Quizzes_practice;
  
  import java.awt.Color;
  import java.awt.FlowLayout;
  import java.awt.GridLayout;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  import javax.swing.JTextField;
  
  
  public class TextField1 extends JFrame {
      private JPanel mainpanel;
      private JLabel text; 
      private JTextField mytext;
      private JTextField bg;
  
  
      public TextField1(){
          setLayout(new GridLayout(2,0));
          JPanel mainpanel = new JPanel();
          JLabel text = new JLabel("Enter value: ");
          JTextField mytext = new JTextField(10);
          JTextField bg = new JTextField(40);
  
  
          add(mainpanel);
          mainpanel.setLayout(new FlowLayout());
          mainpanel.add(text);
          mainpanel.add(mytext);
          mainpanel.add(bg);
          myhand handler = new myhand();
          mytext.addActionListener(handler);
          bg.addActionListener(handler);
  
  
      }
      private class myhand implements ActionListener{
          public void actionPerformed (ActionEvent event){
  
  
                  int a2 = Integer.parseInt(event.getActionCommand());
                  Color mycol= new Color(a2);
                  mainpanel.setBackground(mycol);
  
  
  
          }
      }
  
  
  }
  </code></pre>
  
  <p>the error i'm getting is </p>
  
  <pre><code>Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
      at Quizzes_practice.TextField1$myhand.actionPerformed(TextField1.java:47)
      at javax.swing.JTextField.fireActionPerformed(Unknown Source)
      at javax.swing.JTextField.postActionEvent(Unknown Source)
      at javax.swing.JTextField$NotifyAction.actionPerformed(Unknown Source)
      at javax.swing.SwingUtilities.notifyAction(Unknown Source)
      at javax.swing.JComponent.processKeyBinding(Unknown Source)
      at javax.swing.JComponent.processKeyBindings(Unknown Source)
      at javax.swing.JComponent.processKeyEvent(Unknown Source)
      at java.awt.Component.processEvent(Unknown Source)
      at java.awt.Container.processEvent(Unknown Source)
      at java.awt.Component.dispatchEventImpl(Unknown Source)
      at java.awt.Container.dispatchEventImpl(Unknown Source)
      at java.awt.Component.dispatchEvent(Unknown Source)
      at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
      at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
      at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
      at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
      at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
      at java.awt.Component.dispatchEventImpl(Unknown Source)
      at java.awt.Container.dispatchEventImpl(Unknown Source)
      at java.awt.Window.dispatchEventImpl(Unknown Source)
      at java.awt.Component.dispatchEvent(Unknown Source)
      at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
      at java.awt.EventQueue.access$200(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.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
      at java.awt.EventQueue$4.run(Unknown Source)
      at java.awt.EventQueue$4.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)
  </code></pre>