https://www.reddit.com/r/javahelp/comments/18w1akm/capitalize_non_az_characters_javafx_custom_text/

package net.typho.pnegative.utils;

import javafx.geometry.Point2D;
import javafx.geometry.Rectangle2D;
import javafx.geometry.VPos;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
import javafx.scene.text.Font;
import javafx.scene.text.TextAlignment;
import net.typho.pnegative.PNegative;
import net.typho.pnegative.Palette;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class TextBox implements SelectableUIElement {
    private Box box;
    private List<String> text;
    private Font font;
    private int cursorPos;

    public TextBox(Box box, Font font) {
        this.box = box;
        this.font = font;
        text = new ArrayList<>();
        cursorPos = 0;
    }

    @Override
    public void draw(GraphicsContext gc) {
        Rectangle2D bounds = box.get(PNegative.uiScale);

        gc.setFill(Palette.a4());
        gc.fillRect(bounds.getMinX(), bounds.getMinY(), bounds.getWidth(), bounds.getHeight());

        gc.setFill(Palette.a5());
        gc.fillRect(bounds.getMinX() + PNegative.uiScale, bounds.getMinY() + PNegative.uiScale, bounds.getWidth() - PNegative.uiScale * 2, bounds.getHeight() - PNegative.uiScale * 2);

        StringBuilder text = new StringBuilder();

        for (String s : this.text) {
            text.append(s);
        }

        gc.setFill(Palette.b2());
        gc.setFont(new Font(font.getName(), font.getSize() * PNegative.uiScale));
        gc.setTextAlign(TextAlignment.LEFT);
        gc.setTextBaseline(VPos.CENTER);
        gc.fillText(String.valueOf(text), bounds.getMinX() + PNegative.uiScale * 2, (bounds.getMinY() + bounds.getHeight() / 2));
    }

    @Override
    public boolean contains(Point2D point) {
        return box.get(PNegative.uiScale).contains(point);
    }

    @Override
    public void handle(KeyEvent event) {
        switch (event.getCode()) {
            case ENTER:
                PNegative.selectedItem = null;
                return;
            case LEFT:
                if (cursorPos - 1 >= 0) {
                    cursorPos -= 1;
                }
                return;
            case RIGHT:
                if (cursorPos + 1 <= text.size() - 1) {
                    cursorPos += 1;
                }
                return;
            case BACK_SPACE:
                if (cursorPos - 1 >= 0) {
                    text.remove(cursorPos - 1);
                    cursorPos -= 1;
                }
                return;
        }

        int c = event.getCode().getCode();

        if (c >= 33 && c <= 126) {
            if (event.isShiftDown()) {
                text.add(cursorPos, Character.toString(Character.toUpperCase(c)));
            } else {
                text.add(cursorPos, Character.toString(Character.toLowerCase(c)));
            }

            cursorPos += 1;
        }
    }
}