Inputting unicode characters into JTextField

In most situations I can enter Unicode characters by typing ctrl-shift-u followed by the hexadecimal character code. So for instance by typing ctrl-shift-u 2264 here in the browser I get "≤". I am using Linux; Windows has a comparable way of entry by holding alt and entering the decimal code for the character on the numpad. I don't know macOS well but I assume there is a similar keyboard combination for entering Unicode characters by code.

When I run a Java program, in particular I am using this demo program from Oracle, none of these methods of entering a Unicode character into a JTextField by keyboard seem to work. I can copy the characters in from another applications (gedit) and paste them in. But I haven't found a way either by trial or by searching the interwebs to type them in directly.

Is there a way to make the JTextField control accept (presumably os-specific) key codes for Unicode characters?

Steps to reproduce the issue on Linux

1. Compile and run the following application:

import javax.swing.*;
class JTextFieldExample
{
    public static void main(String args[]) {
        JFrame f = new JFrame("JTextField Example");
        JTextField t = new JTextField("");
        t.setBounds(10, 10, 400, 30);
        f.add(t);
        f.setSize(420,90);
        f.setLayout(null);
        f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        f.setVisible(true);
    }
}

2. Press ctrl + shift + U 2264 + Enter.
3. You will see that the "≤" character fails to make it into the JTextField.
4. Now press the same key sequence into a text editor, select and copy the "≤" character to your clipboard, and then paste it into the JTextField. You will see that it gets entered correctly there, proving that the JTextField can in fact display that character, but it fails to process the key sequence correctly.

edit: since many seem to be interested, I am using Debian Testing (Trixie) updated as of 2024.08.22.

$ java --version
openjdk 23-ea 2024-09-17
OpenJDK Runtime Environment (build 23-ea+34-Debian-1)
OpenJDK 64-Bit Server VM (build 23-ea+34-Debian-1, mixed mode, sharing)

The information on windows was sent to me by another user, and I have no information on macs. I hope this information is helpful.