UpperLowerCaseConverter

/**
 * Sebuah program yang dapat format text menjadi Upper-case, Lower-case
 * maupun case tersebut di invert
 *
 * @author Daffa Tristan Firdaus
 * @version 14 Januari 2021
 */

import javax.swing.*;
import javax.swing.JFrame;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class UpperLowerCaseConverter extends JFrame
{
    private JButton button1, button2, button3, button4, button5, button6;
    private JTextArea textarea1, textarea2;
    public static String invertCase(String str)
    {
        char[] chars = str.toCharArray();
        for (int i = 0; i < chars.length; i++) {
            chars[i] = Character.isUpperCase(chars[i])
                                ? Character.toLowerCase(chars[i])
                                : Character.toUpperCase(chars[i]);
        }
        return new String(chars);
    }
    public UpperLowerCaseConverter() {
        JFrame f = new JFrame("Upper-case Lower-case Converter");
        f.setTitle("Upper-case Lower-case Converter");
        f.setSize(500,400);

        JPanel contentPane = new JPanel(null);
        contentPane.setPreferredSize(new Dimension(500,400));
        contentPane.setBackground(Color.DARK_GRAY);

        button1 = new JButton();
        button1.setBounds(18,176,120,35);
        button1.setBackground(new Color(214,217,223));
        button1.setForeground(new Color(0,0,0));
        button1.setEnabled(true);
        button1.setFont(new Font("sansserif",0,12));
        button1.setText("Upper-Case");
        button1.setVisible(true);
        button1.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String str = textarea1.getText();
                textarea2.setText(str.toUpperCase());
            }
        });

        button2 = new JButton();
        button2.setBounds(145,176,120,35);
        button2.setBackground(new Color(214,217,223));
        button2.setForeground(new Color(0,0,0));
        button2.setEnabled(true);
        button2.setFont(new Font("sansserif",0,12));
        button2.setText("Lower-Case");
        button2.setVisible(true);
        button2.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String str = textarea1.getText();
                textarea2.setText(str.toLowerCase());
            }
        });

        button3 = new JButton();
        button3.setBounds(404,280,90,35);
        button3.setBackground(new Color(214,217,223));
        button3.setForeground(new Color(0,0,0));
        button3.setEnabled(true);
        button3.setFont(new Font("sansserif",0,12));
        button3.setText("Copy");
        button3.setVisible(true);
        button3.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textarea2.selectAll();
                textarea2.copy();
            }
        });

        button4 = new JButton();
        button4.setBounds(404,75,90,35);
        button4.setBackground(new Color(214,217,223));
        button4.setForeground(new Color(0,0,0));
        button4.setEnabled(true);
        button4.setFont(new Font("sansserif",0,12));
        button4.setText("Paste");
        button4.setVisible(true);
        button4.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textarea1.paste();
            }
        });

        button5 = new JButton();
        button5.setBounds(273,176,120,35);
        button5.setBackground(new Color(214,217,223));
        button5.setForeground(new Color(0,0,0));
        button5.setEnabled(true);
        button5.setFont(new Font("sansserif",0,12));
        button5.setText("Invert Case");
        button5.setVisible(true);
        button5.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String str = textarea1.getText();
                textarea2.setText(invertCase(str));
            }
        });

        button6 = new JButton();
        button6.setBounds(404,30,90,35);
        button6.setBackground(new Color(214,217,223));
        button6.setForeground(new Color(0,0,0));
        button6.setEnabled(true);
        button6.setFont(new Font("sansserif",0,12));
        button6.setText("Clear");
        button6.setVisible(true);
        button6.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textarea1.setText("");
            }
        });

        textarea1 = new JTextArea();
        textarea1.setBounds(18,18,380,150);
        textarea1.setBackground(new Color(255,255,255));
        textarea1.setForeground(new Color(0,0,0));
        textarea1.setEnabled(true);
        textarea1.setFont(new Font("sansserif",0,12));
        textarea1.setText("Input");
        textarea1.setBorder(BorderFactory.createBevelBorder(1));
        textarea1.setVisible(true);

        textarea2 = new JTextArea();
        textarea2.setBounds(18,220,380,150);
        textarea2.setBackground(new Color(255,255,255));
        textarea2.setForeground(new Color(0,0,0));
        textarea2.setEnabled(true);
        textarea2.setFont(new Font("sansserif",0,12));
        textarea2.setText("Output");
        textarea2.setBorder(BorderFactory.createBevelBorder(1));
        textarea2.setVisible(true);

        contentPane.add(button1);
        contentPane.add(button2);
        contentPane.add(button3);
        contentPane.add(button4);
        contentPane.add(button5);
        contentPane.add(button6);
        contentPane.add(textarea1);
        contentPane.add(textarea2);

        f.add(contentPane);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.pack();
        f.setVisible(true);
    }

    public static void main(String[] args){
        UpperLowerCaseConverter ulcc = new UpperLowerCaseConverter();
    }
}