What does it mean: The serializable class does not declare a static final serialVersionUID field? [duplicate]

Question

I have the warning message given in the title. I would like to understand and remove it. I found already some answers on this question but I do not understand these answers because of an overload with technical terms. Is it possible to explain this issue with simple words?

P.S. I know what OOP is. I know what is object, class, method, field and instantiation.

P.P.S. If somebody needs my code it is here:

import java.awt.*; import javax.swing.*;   public class HelloWorldSwing extends JFrame {          JTextArea m_resultArea = new JTextArea(6, 30);          //====================================================== constructor         public HelloWorldSwing() {             //... Set initial text, scrolling, and border.             m_resultArea.setText("Enter more text to see scrollbars");             JScrollPane scrollingArea = new JScrollPane(m_resultArea);             scrollingArea.setBorder(BorderFactory.createEmptyBorder(10,5,10,5));              // Get the content pane, set layout, add to center             Container content = this.getContentPane();             content.setLayout(new BorderLayout());             content.add(scrollingArea, BorderLayout.CENTER);             this.pack();         }          public static void createAndViewJFrame() {             JFrame win = new HelloWorldSwing();             win.setTitle("TextAreaDemo");             win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);             win.setVisible(true);         }          //============================================================= main         public static void main(String[] args) {             SwingUtilities.invokeLater(new Runnable(){                 public void run(){                     createAndViewJFrame();                 }             });         }  } 

Answer 1

From the javadoc:

The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of the corresponding sender's class, then deserialization will result in an InvalidClassException. A serializable class can declare its own serialVersionUID explicitly by declaring a field named "serialVersionUID" that must be static, final, and of type long:

You can configure your IDE to:

• ignore this, instead of giving a warning.
• autogenerate an id

As per your additional question "Can it be that the discussed warning message is a reason why my GUI application freeze?":

No, it can't be. It can cause a problem only if you are serializing objects and deserializing them in a different place (or time) where (when) the class has changed, and it will not result in freezing, but in InvalidClassException.