Error in here , can't find it by myself .
If someone will find it ,please let me know.

package flow.layout;

import java.awt.*;

import javax.swing.*;

public class Flow {


JPanel windowContent;
JLabel label1;
JLabel label2;
JLabel label3;

Flow () {


windowContent = new JPanel();

FlowLayout fl = new FlowLayout();
windowContent.setLayout(fl);

label1 = new JLabel(" test 1");
label2 = new JLabel (" test 2");
label3 = new JLabel (" test 3 ");
windowContent.add(label1);
windowContent.add(label2);
windowContent.add(label3);

JFrame frame = new JFrame("My test" );

frame.setContentPane(windowContent);
frame.pack();



frame.setVisible(true);
}
public static void main(String[] args){
new Flow() ;
}

}

package com.practicaljava.lesson30;
import java.awt.*;
import javax.swing.*;

public class Flow {

JPanel windowContent;
JLabel label1;
JLabel label2;
JLabel label3;

Flow () {
windowContent = new JPanel();
FlowLayout fl = new FlowLayout();
windowContent.setLayout(fl);
label1 = new JLabel(" test 1");
label2 = new JLabel (" test 2");
label3 = new JLabel (" test 3 ");
windowContent.add(label1);
windowContent.add(label2);
windowContent.add(label3);

JFrame frame = new JFrame("My test" );

frame.setContentPane(windowContent);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args){
new Flow() ;
}
}