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Java Label Image.txt

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Zvirata extends JFrame{
    //Container obsah;
    String[] zvirata = { "Pes", "Kočka", "Prase"};
    JComboBox cb;
    JLabel l1 = new JLabel();
    ImageIcon obrazek;
    public Zvirata(){
        init();
        obsah();
        setVisible(true);
    }
    public void init(){
        setTitle("Zvířata");
        setSize(515,475);
        setLocationRelativeTo(null);
        /*obsah = getContentPane();//obsah formuláře
        obsah.setBackground(Color.RED);*/
        setLayout(new FlowLayout());
        setDefaultCloseOperation(3);
    }
    @SuppressWarnings("unchecked")
    public void obsah(){
        cb = new JComboBox(zvirata);
        obrazek = new ImageIcon("Pes.png");
        l1.setIcon(obrazek);
        add(cb);
        add(l1);
        cb.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
                String s = cb.getSelectedItem().toString();
                obrazek = new ImageIcon(s+".png");
                l1.setIcon(obrazek);
            }
        });
    }
    public static void main(String[] args){
        Zvirata z = new Zvirata();
    }
}