// Program: When pushing the JButton the user input a text and JButtons title change to that text. This text should be save when main is activated another time.import javax.swing.*;import java.awt.event.*;import java.util.prefs.*;public class Storing extends JFrame{ private JButton button; private Preferences root; // Should store the text on JButton private String text = "Standard"; // Text on JButton // Constructor public Storing(){ // root.put("key",text); <- Thought NullPointerException was becouse "key" dident exist. But that wasent the case // Trying to put "text" to the users input // >>>>>>>>>>>>>>>>> This gives NullPointerException: null <<<<<<<<<<<<<<<< text = root.get("key","Standard"); // API: get(String key, String def) // Creating and adding button button = new JButton(text); ActionListener change = new Change(); button.addActionListener(change); add(button); // JFrame settings setSize(200,200); setVisible(true); } // Listener for the "button" public class Change implements ActionListener{ public void actionPerformed(ActionEvent e){ // Change the text on the button to the input from user text = JOptionPane.showInputDialog("New key setting: ",text); button.setText(text); // Trying to add the input to the "Preferences" root.put("key",text); } } // Run program public static void main(String[] args){ new Storing(); }}