Shows a faster, better way of updating a set of string labels. The comments have a slower version that completely redraws the screen and is massively slower: > 30 ms vs 0-2 ms

JavaFXLayoutTimingTest.java

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.time.Duration;
import java.time.Instant;
import java.util.ArrayList;
import java.util.List;


public class JavaFXLayoutTimingTest extends Application {
    private static Instant start;

    private int reloadCount = 0;

    private final int pageSize = 50;
    private List<Label> labels = new ArrayList<>(pageSize);

    private void logTimeSinceStart() {
        System.err.println("Reloaded label strings: " + Duration.between(start, Instant.now()).toMillis());
    }

    /*
    about 35 ms to run this!
    public void reloadEntireStage(Stage stage) {
        System.err.println("Reloading page at " + Instant.now());
        

        start = Instant.now();

        root = new VBox();
        Button button = new Button("I am a banana");

        List<Label> labels = new ArrayList<>(pageSize);
        for(int i = 1; i <= pageSize; i++) {
            labels.add(new Label("Label " + (reloadCount*pageSize + i)));
        }

        root.getChildren().add(button);
        root.getChildren().addAll(labels);
        button.setOnAction(ae -> {
            reloadCount++;
            reloadEntireStage(stage);
        });

        scene.setRoot(root);
        stage.setScene(scene);

    }
    */

    /* 0-2 milliseconds to run this!!! */
    private void updateLabelStrings() {
        start = Instant.now();

        final int pageSize = 50;

        start = Instant.now();

        for (int i = 0; i < pageSize; i++) {
            labels.get(i).setText("Label " + (reloadCount * pageSize + i));
        }

        logTimeSinceStart();
    }

    @Override
    public void start(Stage stage) {
        stage.setTitle("Web View");

        VBox root = new VBox();
        Button button = new Button("I am a banana");

        Scene scene = new Scene(root, 400, 900);
        scene.setOnKeyPressed(event -> {
            switch (event.getCode()) {
                case LEFT:
                    reloadCount--;
                    updateLabelStrings();
                    break;
                case RIGHT:
                    reloadCount++;
                    updateLabelStrings();
                    break;
            }
        });

        root.getChildren().add(button);
        root.getChildren().addAll(labels);
        button.setOnAction(ae -> {
            reloadCount++;
            updateLabelStrings();
        });

        for (int i = 0; i < pageSize; i++) {
            labels.add(new Label("Label " + (reloadCount * pageSize + i)));
        }

        root.getChildren().addAll(labels);

        scene.setRoot(root);
        stage.setScene(scene);
        stage.show();
    }

    public static void main(String[] args) {
        start = Instant.now();
        launch(args);
    }
}