如何从JTextField设置字体TextArea的大小并使用RadioButoon更改样式文本

Question

当我使用JRadioButton设置JTextArea的字体时，我陷入了困境，我只是设置了一个组，设置了粗体和斜体文本。而且，当我输入int编号时，我无法设置JTextArea中接收JTextField的文本大小。我的DoExit方法不起作用。我已经使用JComboBox设置了更改文本的颜色，但是我无法设置大小和样式。

import javax.swing.JFrame;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextArea;
import javax.swing.JTextField;
/**
*
* @author anmanh
*/
public class BTH2 extends JFrame implements ActionListener{

JLabel jlTiitle,jlND, jlColor, jlStyle, jlSize;
JTextField  jtxSize;
JTextArea jtaText;
JComboBox jcbColor;
JRadioButton jrbBold,jrbItalic;
JButton jbtClear, jbtExit ;
ButtonGroup btn;

public BTH2(){
    this.setSize(800, 250);
    this.setTitle("Test 3");
    this.setVisible(true);

    Font f1 =new Font("Arial", Font.BOLD, 14);
    Font f2 =new Font("Arial", Font.ITALIC, 14);

    jlTiitle = new JLabel("Custom text");
    jlTiitle.setFont(new Font("Time New Roman", Font.BOLD, 20));
    jlTiitle.setForeground(Color.BLUE);

    jlND = new JLabel("Enter any text: ");
    jlND.setFont(new Font("Arial", Font.BOLD, 14));
    jlND.setForeground(Color.black);

    jlColor = new JLabel("Select color: ");
    jlColor.setFont(new Font("Arial", Font.BOLD, 14));
    jlColor.setForeground(Color.black);

    jlStyle = new JLabel("Select font: ");
    jlStyle.setFont(new Font("Arial", Font.BOLD, 14));
    jlStyle.setForeground(Color.black);

    jlSize = new JLabel("Enter text size: ");
    jlSize.setFont(new Font("Arial", Font.BOLD, 14));
    jlSize.setForeground(Color.black);

    jtaText = new JTextArea("Enter any text ");
    jtaText.setPreferredSize(new Dimension(180, 160));
    jtaText.setFont(f1);

    jtxSize = new JTextField();
    jtxSize.setColumns(10);
    jtxSize.setFont(f1);

    jcbColor = new JComboBox();
    jcbColor.setFont(f1);
    jcbColor.addItem("  Mau Do          ");
    jcbColor.addItem("  Mau Xanh          ");
    jcbColor.addItem("  Mau Den         ");
    jcbColor.addItem("  Mau Vang          ");
    jcbColor.addItemListener(new ItemListener() {
        @Override
        public void itemStateChanged(ItemEvent e) {
            if (jcbColor.getSelectedIndex() == 0) {
                jtaText.setForeground(Color.RED);
            }

            if (jcbColor.getSelectedIndex() == 1) {
                 jtaText.setForeground(Color.GREEN);
            }

            if (jcbColor.getSelectedIndex() == 2) {
                 jtaText.setForeground(Color.BLACK);
            }

            if (jcbColor.getSelectedIndex() == 3) {
                 jtaText.setForeground(Color.YELLOW);
            }

        }
    });

    jbtClear = new JButton("Clear");
    jbtClear.setFont(f2);
    jbtClear.setForeground(Color.BLACK);
    jbtClear.setBackground(Color.gray);
    jbtClear.addActionListener(this);

    jbtExit = new JButton("Thoat");
    jbtExit.setFont(f2);
    jbtExit.setForeground(Color.BLACK);
    jbtExit.setBackground(Color.gray);
    jbtClear.addActionListener(this);

    jrbBold = new JRadioButton("Chu dam");
    jrbBold.setFont(f1);
    jrbItalic = new JRadioButton("Chu nghieng");
    jrbItalic.setFont(f2);
    btn = new ButtonGroup();
    btn.add(jrbBold);
    btn.add(jrbItalic);
    if(jrbBold.isSelected()){
        Font font1 = new Font("Arial", Font.BOLD, 20);
        jtaText.setFont(font1);

   //     jtaText.setFont(jtaText.getText(), Font.BOLD); 
    }
     if(jrbItalic.isSelected()){
       Font font2 = new Font("Arial", Font.ITALIC, 20);
       jtaText.setFont(font2);
    }

    JPanel pNorth = new JPanel();
    pNorth.add(jlTiitle);
    this.add(pNorth, BorderLayout.NORTH);

    JPanel pSouth = new JPanel();
    pSouth.setLayout(new FlowLayout());
    pSouth.add(jbtClear);
    pSouth.add(jbtExit);
    this.add(pSouth, BorderLayout.SOUTH);

    JPanel pWest = new JPanel();
    pWest.setLayout(new GridLayout(1, 2));
    pWest.add(jlND);
    pWest.add(jtaText);
    this.add(pWest, BorderLayout.WEST);

    JPanel pEast = new JPanel();
    pEast.setLayout(new GridLayout(3, 2));
    pEast.add(jlColor);
    pEast.add(jcbColor);
    pEast.add(jlStyle);

    JPanel j1 = new JPanel();
    j1.setLayout(new FlowLayout());
    j1.add(jrbBold);
    j1.add(jrbItalic);
    pEast.add(j1);
    pEast.add(jlSize);
    pEast.add(jtxSize);
    this.add(pEast, BorderLayout.EAST);       

    //Set size Jtextarea from jTextfield
    jtaText.setFont(jtxSize.getFont());
}


@Override
public void actionPerformed(ActionEvent e) {
     if (e.getSource() == jbtClear) {
        doClear();
    }

    if (e.getSource() == jbtExit) {
        doExit();
    }

}

void doClear(){
    jtaText.setText(" ");
    jtxSize.setText(" ");
}

void doExit() {
     if (JOptionPane.showConfirmDialog(null, "Do you want to exit?", 
"Notify", JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION) {
                System.exit(0);
}
}

void checkInput(){
    //Chech empty

    if (jtxSize.getText().equals("")) {
        JOptionPane.showMessageDialog(null, "Ban chua nhap 
size","Error",JOptionPane.OK_OPTION);
        return;
    }

    //check type of input
    if (!isNumber(jtxSize.getText(), 0)) {
        JOptionPane.showMessageDialog(null, "Ban chua nhap size la 
Integer","Error",JOptionPane.OK_OPTION);
        return;
    }       
}

 boolean isNumber(String number, int type){
    try{
        if (type == 0) {
            int n = Integer.parseInt(number);
        }else{
            double n = Double.parseDouble(number);
        }

    } catch (Exception e){
        return false;
    }
    return true;
}
}