title: JTextField.getText() returns null value even if it has content inside
body: <p>I have a portion of code that takes the text of a TextField (there are two TextFields actually, but the user can use only one at a time) and search it into a file stored into the terminal. The problem is that I always get a null string, even when there is text into one of the TextFields...
  This is the code (the assignation is on the method actionPerformed(): </p>
  
  <pre><code>import javax.swing.*;
  import java.awt.*;
  import java.awt.event.*;
  import java.io.*;
  
  public class Search implements ActionListener{
  JFrame frame;
  JButton click;
  JLabel comando, carico;
  JTextField textv, text;
  JTextArea res;
  String pathFile = "C:\\Log.txt";
  String str= new String();
  
  Search(){
  
      frame = new JFrame("Search");
      frame.setSize(400, 200);
      frame.setVisible(true);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setLayout(new GridLayout(1,2));
      frame.setResizable(false);
      JPanel panel = new JPanel();
      panel.setLayout(new GridLayout(7,1));
      click = new JButton("Cerca");
      comando = new JLabel("Comando");
      carico = new JLabel("A carico di:");
      textv = new JTextField("");
      text = new JTextField("");
      res = new JTextArea("");
      panel.add(comando);
      panel.add(textv);
      panel.add(carico);
      panel.add(text);
      panel.add(click);
      res.setLineWrap(true);
      res.setWrapStyleWord(true);
      res.setBorder(BorderFactory.createEmptyBorder(4, 4, 4, 4));
  
      JScrollPane scroller = new JScrollPane(res);
      scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
      panel.add(scroller);
      frame.add(panel);
      click.addActionListener(this);      
      click.setSize(70, 35);      
      frame.setVisible(true);
  
  }
  
  public void actionPerformed (ActionEvent e){
      if(e.getSource()==click){
          res.setText(null);
          if(textv != null) {cercaStringa(pathFile, textv.getText().toString());}
          else {cercaStringa(pathFile, text.getText().toString());}
      }
  }
  
  public void cercaStringa(String pathFile, String stringa){
      try {
          BufferedReader in = new BufferedReader(new FileReader(pathFile));
          String line = new String();
          while((line = in.readLine())!=null) {   
              if(line.contains(stringa)){
                  res.append(line);
                  res.append("\n");
                  }
          }
      }
      catch(IOException ex) { ex.printStackTrace();}
      }
  
  
  
  public static void main (String[] args){
      new Search();
  }
  </code></pre>
  
  <p>}</p>
  
  <p>I'm really going to throw everything outside the window cause I know the solution is simple but I can't get it...</p>