Instantiate a class created during runtime

Question

I created the demo below that does the following:

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1. User writes their class in the JTextArea provided.
2. Clicks on the Instantiate Class JButton to create a java file regarding the class created by the user.
3. Clicks on the Run JButton in order to actually use the created class (code commented).

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I don't know if this is the best approach (to creat a java file) to run a class created during runtime. However, in my actual project, I do need these created classes in .java files.

I understand that Eclipse does not allow the commented part because at compiling time the compiler has no idea of what myClass is. How can I do this?

Code:

import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class Main {

    public static void main(String[] args) {
        JFrame frame = new JFrame("Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        frame.setLayout(new GridLayout(1,3));

        JTextArea editor = new JTextArea();
        editor.setPreferredSize(new Dimension(400,400));
        editor.setTabSize(4);
        editor.setText("public class myClass {\n" + 
                "\tpublic int myValue;\n" + 
                "\t\n" + 
                "\tpublic myClass(int value){\n" + 
                "\t\tmyValue = value;\n" + 
                "\t}\n" + 
                "\t\n" + 
                "\tpublic int getValue() {\n" + 
                "\treturn myValue;\n" + 
                "\t}\n" + 
                "}");

        JButton instantiate = new JButton("Instantiate class");
        JButton run = new JButton("Run");

        frame.getContentPane().add(editor);
        frame.getContentPane().add(instantiate);
        frame.getContentPane().add(run);
        frame.pack();
        frame.setVisible(true);

        instantiate.addActionListener(new ActionListener() { 
            public void actionPerformed(ActionEvent e) { 
                try {
                    PrintWriter out = new PrintWriter("src/myClass.java");
                    out.println(editor.getText());
                    out.close();
                } catch (FileNotFoundException e1) {
                    e1.printStackTrace();
                }
            } 
        });

        run.addActionListener(new ActionListener() { 
            public void actionPerformed(ActionEvent e) { 
                //This is what I want to do

                //myClass myObject = new myClass(4);
                //System.out.println("My value is: " + myObject.getValue());
            } 
        });

    }

}