DoubleBox with numeric key handling in GWT

package ru.mitrakov.self.adsbidder.client.ui;

import java.util.*;
import java.text.ParseException;
import com.google.gwt.dom.client.Document;
import com.google.gwt.event.dom.client.KeyDownHandler;
import com.google.gwt.i18n.client.NumberFormat;
import com.google.gwt.text.shared.AbstractRenderer;
import com.google.gwt.user.client.ui.ValueBox;
import static com.google.gwt.event.dom.client.KeyCodes.*;

@SuppressWarnings("WeakerAccess")
public class DoubleBoxEx extends ValueBox<Double> {
    static protected NumberFormat renderFormat = NumberFormat.getFormat("####.##");
    static protected NumberFormat parseFormat = NumberFormat.getFormat("####.##");

    protected KeyDownHandler doubleHandler() {
        final Set<Integer> allowedKeys = new HashSet<>(Arrays.asList(
                KEY_ONE, KEY_NUM_ONE,
                KEY_TWO, KEY_NUM_TWO,
                KEY_THREE, KEY_NUM_THREE,
                KEY_FOUR, KEY_NUM_FOUR,
                KEY_FIVE, KEY_NUM_FIVE,
                KEY_SIX, KEY_NUM_SIX,
                KEY_SEVEN, KEY_NUM_SEVEN,
                KEY_EIGHT, KEY_NUM_EIGHT,
                KEY_NINE, KEY_NUM_NINE,
                KEY_ZERO, KEY_NUM_ZERO,
                KEY_LEFT, KEY_RIGHT,
                KEY_END, KEY_HOME,
                KEY_DELETE, KEY_BACKSPACE,
                KEY_ENTER, KEY_MAC_ENTER,
                KEY_TAB,
                KEY_NUM_MINUS, 173, // 173 is "-"
                KEY_NUM_PERIOD, 190 // 190 is "."
                // note that we filter out code 188 (",") because it's a group separator (1,000,000) that may confuse users
        ));
        return event -> {
            boolean isAllowedKey = allowedKeys.contains(event.getNativeKeyCode());
            boolean isPaste1 = event.isControlKeyDown() && event.getNativeKeyCode() == KEY_V;
            boolean isPaste2 = event.isShiftKeyDown() && event.getNativeKeyCode() == KEY_INSERT;
            if (!isAllowedKey && !isPaste1 && !isPaste2)
                cancelKey();
            // note that mentioned above handling is not exhaustive: user still can copy-paste using context menu
        };
    }

    public DoubleBoxEx() {
        super(Document.get().createTextInputElement(), new AbstractRenderer<Double>() {
                public String render(Double value) { return renderFormat.format(value); }
            }, text -> {
                try {
                    return parseFormat.parse(text.toString().replace(',', '.'));
                } catch (NumberFormatException e) {
                    throw new ParseException(e.getMessage(), 0); // throwing is necessary to get ValueBox<T> working
                }
            }
        );

        setStyleName("am-DoubleBox");
        addKeyDownHandler(doubleHandler());
        getElement().setPropertyString("placeholder", "0.0");
    }
}