This looks like linux-only issue.

Code:


import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.input.Clipboard;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class JavaApplication52 extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        Button button = new Button("clear clipdoard");
        button.setOnAction(new EventHandler<ActionEvent>() {

            @Override
            public void handle(ActionEvent t) {
                Clipboard.getSystemClipboard().clear();
            }
        });

        TextField tf = new TextField("Some text");

        VBox vb = new VBox();
        vb.getChildren().addAll(button, tf);

        Scene scene = new Scene(vb, 300, 300);
        stage.setScene(scene);
        stage.show();
    }
}

Click on button and click with right mouse button on the text field.

Paste button is disabled on windows, and active on linux.