import javax.swing.*;
import java.awt.event.*;
class TextFieldAndButton 
{
    public static void main(String[] args) 
    {
        JFrame f=new JFrame();
        JTextField text=new JTextField(20);
        final JButton b=new JButton("Check");
        b.setEnabled(false);
        text.addKeyListener(new KeyAdapter(){
      public void keyPressed(KeyEvent keyEvent) {
        b.setEnabled(true);
      }
      public void keyReleased(KeyEvent keyEvent) {
        b.setEnabled(true);
      }
      public void keyTyped(KeyEvent keyEvent) {
        b.setEnabled(true);
      }
    });
    text.setBounds(10,10,150,20);
    b.setBounds(10,30,100,20);
    f.setLayout(null);
    f.add(text);
    f.add(b);
    f.setVisible(true);
    f.setSize(300,100);
  }
}