Java GUI sample

This is a Java GUI sample. Regarding the Java GUI, there are some samples that are completely described in the main class, and I remember having difficulty finding a practical usage, so I implemented a group of GUI dialogs separately from the main class. Share here.

１．swing.JOptionPane InfoDialog

This is a general-purpose dialog.

main.java

public class Main {
    public static void main(String[] args) {
        InfoDialog.showDialog("Please select a file(.xlsx)。");
       }
}

InfoDialog.java

import javax.swing.JOptionPane;

class InfoDialog {

	public static void showDialog(String msg) {
		JOptionPane.showMessageDialog(null, msg,"Take it",JOptionPane.INFORMATION_MESSAGE);
	}
}

When using this method, specify the character string you want to display in the dialog for the argument String. Here, "Please select a file (.xlsx)." I think the 2nd-4th arguments of the showMessageDialog method are understandable, but the first one takes parentComponent as an argument. I couldn't figure out what the ~~ parentComponent was, but ~~ basic null should be fine.

If you want to select "Yes" or "No", use the showConfirmDialog method instead of showMessageDialog.

ErrorDialog Just change the 4th argument of ShowMessageDialog from INFORMATION_MESSAGE, to ERROR_MESSAGE, and nothing else will change.

main.java

public class Main {
    public static void main(String[] args) {
        InfoDialog.ErrorDialog(".xlsx is unspecified. I'm done.");
       }
}

ErrorDialog.java

import javax.swing.JOptionPane;

class ErrorDialog {

	public static void showDialog(String msg) {
		JOptionPane.showMessageDialog(null, msg,"Take it",JOptionPane.ERROR_MESSAGE);
	}
}

２．awt.FileDialog

A dialog that lets the user select a file.

Main.java

public class Main {
	public static void main(String[] args) {
		new WindowTest();
        File file = new File(WindowTest.dir + WindowTest.fileName);
       }
}

WindowTest.java

import java.awt.FileDialog;
import java.awt.Frame;
import java.awt.event.WindowListener;

class WindowTest extends Frame implements WindowListener {
	static String dir;
	static String fileName;

	WindowTest() {
		FileDialog fileDialog = new FileDialog(this);
		fileDialog.setVisible(true);
		this.dir = fileDialog.getDirectory();
		this.fileName = fileDialog.getFile();

		if (fileName == null) {
			ErrorDialog.showDialog(".xlsx is unspecified. I'm done.");
			System.exit(0);
		}
	}

	public void windowActivated(java.awt.event.WindowEvent e) {
	}
	public void windowClosed(java.awt.event.WindowEvent e) {
	}
	public void windowClosing(java.awt.event.WindowEvent e) {
		System.exit(1);
	}
	public void windowDeactivated(java.awt.event.WindowEvent e) {
	}
	public void windowDeiconified(java.awt.event.WindowEvent e) {
	}
	public void windowIconified(java.awt.event.WindowEvent e) {
	}
	public void windowOpened(java.awt.event.WindowEvent e) {
	}
}

that's all.