Write a simple JAVA GUI program. The GUI interface needs to contain 1 JLabel and

Question

Write a simple JAVA GUI program. The GUI interface needs to contain 1 JLabel and 4 JButtons. The functionality of the buttons is discussed below. The GUI components need to be contained within a JFrame. Additionally a JPanel should be used to help control the layout of the buttons. Use a GridLayout for the layout manager. The buttons should be displayed in a 2 by 2 grid. Here is an approximate picture for the layout for the components:

                                                   Hello World

                                        Uppercase       Lowercase

                                            New Phrase       Reset

Functionality: Each of the buttons needs to perform a different function.

Uppercase: should display the string of the label in all uppercase letters, use a String method for this - do not hardcode a String in all upper case.

Lowercase: should display the String in the label in all lowercase letters, use a String method for this - do not hardcode a String in all lower case.

New Phrase: should get input from the user via a dialog box. Then place this input into the label. The case buttons will need to be able to alter this string!

Reset: should restore the contents of the label to (exact case): %u201CHello World%u201D

Misc. Notes:

At launch the label of the text should read %u201CHello World%u201D

Make sure to make your jar file executable. This is a GUI program. Assuming everything has been done correctly, when you double click on the jar file%u2019s icon the program should launch!

Explanation / Answer

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class DemoPanel extends JFrame implements ActionListener{
    JLabel content = null;
    public DemoPanel(){
        setSize(400,300);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
   
    public static void main(String args[]){
        DemoPanel p = new DemoPanel();
        p.buildPanel();
    }
   
    public void buildPanel(){
        Container c = getContentPane();
        c.setLayout(new GridLayout(2, 1));
        JPanel labelPanel = new JPanel();
        labelPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
        content = new JLabel("Hello World");
        labelPanel.add(content);
        c.add(labelPanel);
       
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
        JButton uppercase = new JButton("Uppercase");
        uppercase.addActionListener(this);
        buttonPanel.add(uppercase);
        JButton lowercase = new JButton("Lowercase");
        lowercase.addActionListener(this);
        buttonPanel.add(lowercase);
        JButton newPhrase = new JButton("New Phrase");
        newPhrase.addActionListener(this);
        buttonPanel.add(newPhrase);
        JButton reset = new JButton("Reset");
        reset.addActionListener(this);
        buttonPanel.add(reset);
        c.add(buttonPanel);
    }
   
    @Override
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        if(command.equals("Lowercase")){
            content.setText(content.getText().toLowerCase());
        }else if(command.equals("Uppercase")){
            content.setText(content.getText().toUpperCase());
        }else if(command.equals("New Phrase")){
            while(true){
                String newPhrase = JOptionPane.showInputDialog("Enter New Phrase");
                if(newPhrase == null || newPhrase.equals("")){
                    JOptionPane.showMessageDialog(this, "Invalid Input. Please try again.", "Error", JOptionPane.ERROR_MESSAGE);
                    continue;
                }
                content.setText(newPhrase);
                break;
            }
           
        }else if(command.equals("Reset")){
            content.setText("Hello World");
        }
    }
}

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