Trouble Counting Vowels and Consonants

Question

Hey I am trying to create a GUI that has three text fields, one for typing letters into it, the other two counts the vowels and consonants. However, I can't get the code to properly spit out any numbers and whenever I type in letters I get an exception: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class GUI extends JFrame implements KeyListener {
     public int numberOfConsonents = 0;
     public int numberOfVowels = 0;
     public JTextField jtf1;
     public JTextField jtf2;
     public JTextField jtf3;
     public JLabel jl3;
     public JLabel jl2;
     public GUI(){
     JTextField jtf1;
     JTextField jtf2;
     JTextField jtf3;
     jtf1 = new JTextField(20);
     jtf1.addKeyListener(this);
     jtf2 = new JTextField(5);
     jtf3 = new JTextField(5);
     jl2 = new JLabel("Vowels");
     jl3 = new JLabel("Consonants");
     jtf2.setEditable(false);
     jtf3.setEditable(false);
     getContentPane().setLayout(new GridLayout(2,3));
     getContentPane().add(jtf1);
     getContentPane().add(jl2);
     getContentPane().add(jtf2);
     getContentPane().add(jl3);
     getContentPane().add(jtf3);
     public void keyPressed (KeyEvent ke){
          char c = ke.getKeyChar();
          if (Character.isLetter(c)){
               c = Character.toLowerCase(c);
               if(c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u'){
                    numberOfVowels++;
                    jtf3.setText(""+numberOfVowels);
               else{
                    numberOfConsonents++;
                    jtf2.setText(""+numberOfConsonents);
          validate();
//      not used
     public void keyReleased (KeyEvent ke){
     // not used
     public void keyTyped (KeyEvent ke){
     public static void main(String args[]){
          GUI gui = new GUI();
          gui.pack();
          gui.setVisible(true);
          gui.setDefaultCloseOperation(EXIT_ON_CLOSE);
}

Answer 1

In your constructor, don't re-declare the JTextFields. Essentially...
     public GUI(){
     jtf1 = new JTextField(20);
     jtf1.addKeyListener(this);
     jtf2 = new JTextField(5);
     jtf3 = new JTextField(5);
     jl2 = new JLabel("Vowels");
     jl3 = new JLabel("Consonants");
     jtf2.setEditable(false);
     jtf3.setEditable(false);
     getContentPane().setLayout(new GridLayout(2,3));
     getContentPane().add(jtf1);
     getContentPane().add(jl2);
     getContentPane().add(jtf2);
     getContentPane().add(jl3);
     getContentPane().add(jtf3);
     }The reason it's making an error is because you never construct the GLOBAL JTextFields. To access a JTextField globally, if you already have a JTextField with the same name in some method, you have to use this.theNameOfTheThing .