private void initButton(){

        bCancel = new JButton("Cancel");
        bCancel.setSize(dimButt);

        bCancel.setToolTipText("Exit program");
        bCancel.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                frame.dispose();
            }
        });

        frame.add(bCancel);

        bNext = new JButton("Next");
        bNext.setToolTipText("Next word <F12>");
        bNext.setSize(dimButt);
        bNext.setEnabled(false);
        bNext.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if(tabIndex == 0)//Tab <code> TAB_MAIN </code> is chosen
                    index++;
                else if(tabIndex == 1)//Tab <code>TAB_REPETITION</code> is chosen
                    indRepet++;

                setQuestion();
            }
        });

        bAnswer = new JButton("Answer");
        bAnswer.setToolTipText("Insert an answer <F1>");
        bAnswer.setSize(dimButt);
        bAnswer.setEnabled(false);
        bAnswer.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if(tabIndex == 0 && index>-1)//Tab <code> TAB_MAIN </code> is chosen
                    answer.setText(words.get(index).getEWord());
                else if(tabIndex == 1 && indRepet >-1)//Tab <code>TAB_REPETITION</code> is chosen
                    answer.setText(repetitionWords.get(indRepet).getEWord());
            }
        });

        bAddToRepetition = new JButton("Add to repetition");
        bAddToRepetition.setToolTipText("Add current word to repetition list <F5>");
        bAddToRepetition.setSize(dimButt.width + 50, dimButt.height);
        bAddToRepetition.setLocation(378, 114);
        bAddToRepetition.setEnabled(false);
        bAddToRepetition.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                repetitionWords.add(words.get(index));
                numberTotRepetitions.setText(new Integer(repetitionWords.size()).toString());
                showMessage(action, "< " + words.get(index).getEWord() + " > was added");
            }
        });

        bRemoveFromRepetition = new JButton("Remove");
        bRemoveFromRepetition.setToolTipText("Remove current word from repetition list <F8>");
        bRemoveFromRepetition.setSize(dimButt.width+50, dimButt.height);
        bRemoveFromRepetition.setLocation(378, 114);
        bRemoveFromRepetition.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                showMessage(action, "< " + repetitionWords.get(indRepet).getEWord() + " > was removed");
                repetitionWords.remove(indRepet);
                numberTotRepetitions.setText(new Integer(repetitionWords.size()).toString());
                setQuestion();
                if(repetitionWords.isEmpty())
                    bRemoveFromRepetition.setEnabled(false);
            }
        });
        ButtonGroup groupRepetition = new ButtonGroup();
        groupRepetition.add(bAddToRepetition);
        groupRepetition.add(bRemoveFromRepetition);


        frame.add(bNext);
        frame.add(bAnswer);
        mainPanel.add(bAddToRepetition);
        repetPanel.add(bRemoveFromRepetition);
    }