问如何将FileChooser上传的文件保存到项目中的目录中？

EN

import javafx.application.*;
import javafx.geometry.*;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.image.*;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.*;

public class AvatarApp extends Application {
    private static final String APP_DIR = ".avatar";

    private AvatarService avatarService;

    @Override
    public void init() {
        LocalStorage localStorage = new LocalStorage(APP_DIR);
        avatarService = new AvatarService(localStorage);
    }

    @Override
    public void start(Stage stage) throws Exception {
        ImageView avatar = new ImageView(avatarService.getAvatarImage());
        avatar.imageProperty().bind(avatarService.avatarImageProperty());
        avatar.setFitWidth(AvatarService.DIMENSIONS);
        avatar.setFitHeight(AvatarService.DIMENSIONS);
        avatar.setPreserveRatio(true);

        Button changeAvatarButton = new Button("Change...");
        changeAvatarButton.setOnAction(e -> uploadCustomAvatar(stage));

        VBox layout = new VBox(10, avatar, changeAvatarButton);
        layout.setStyle("-fx-background-color: linen; -fx-font-size: 16px");
        layout.setAlignment(Pos.CENTER);
        layout.setPadding(new Insets(10));

        stage.setScene(new Scene(layout));
        stage.show();
    }

    private void uploadCustomAvatar(Stage owner) {
        FileChooser fileChooser = new FileChooser();
        fileChooser.setTitle("Choose your avatar");
        fileChooser.getExtensionFilters().addAll(
                new FileChooser.ExtensionFilter(
                        "PNG Image Files", "*.png"
                )
        );

        File selectedFile = fileChooser.showOpenDialog(owner);
        if (selectedFile != null) {
           try (
                   InputStream inputStream = new BufferedInputStream(
                           Files.newInputStream(selectedFile.toPath())
                   )
           ) {
               avatarService.uploadCustomAvatar(inputStream);
            } catch (IOException ex) {
                System.out.println("Unable to upload avatar");
                ex.printStackTrace();
            }
        }
    }

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

import javafx.application.Platform;
import javafx.beans.property.ReadOnlyObjectProperty;
import javafx.beans.property.ReadOnlyObjectWrapper;
import javafx.scene.image.Image;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.util.Objects;

class AvatarService {
    public static final double DIMENSIONS = 96;

    private static final String DEFAULT_AVATAR_RESOURCE = "Dragon-icon.png";
    private static final String AVATAR_FILENAME = "avatar.png";

    private final Path avatarPath;
    private final ReadOnlyObjectWrapper<Image> avatarImage = new ReadOnlyObjectWrapper<>();

    public AvatarService(LocalStorage localStorage) {
        avatarPath = localStorage.getLocalStoragePath().resolve(AVATAR_FILENAME);

        if (!Files.exists(avatarPath)) {
            copyDefaultAvatar();
        }

        refreshImage();
    }

    private void copyDefaultAvatar() {
        try {
            Files.copy(
                    Objects.requireNonNull(
                            AvatarApp.class.getResourceAsStream(
                                    DEFAULT_AVATAR_RESOURCE
                            )
                    ),
                    avatarPath
            );
        } catch (IOException e) {
            System.out.println("Unable to initialize default avatar");
            e.printStackTrace();
            Platform.exit();
        }
    }

    public void uploadCustomAvatar(InputStream inputStream) {
        try {
            Files.copy(
                    inputStream,
                    avatarPath,
                    StandardCopyOption.REPLACE_EXISTING
            );

            refreshImage();
        } catch (IOException e) {
            System.out.println("Unable to upload custom avatar");
            e.printStackTrace();
        }
    }

    public Image getAvatarImage() {
        return avatarImage.get();
    }


    public ReadOnlyObjectProperty<Image> avatarImageProperty() {
        return avatarImage.getReadOnlyProperty();
    }

    private void refreshImage() {
        avatarImage.set(
                new Image(
                        "file:" + avatarPath.toAbsolutePath()
                )
        );
    }
}

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

class LocalStorage {
    private Path localStoragePath;

    public LocalStorage(String name) {
        try {
            String userDir = System.getProperty("user.home");

            localStoragePath = Paths.get(userDir, name);
            if (!Files.isDirectory(localStoragePath)) {
                Files.createDirectory(localStoragePath);
            }
        } catch (IOException ex) {
            System.out.println("Unable to initialize local storage");
            ex.printStackTrace();
            Platform.exit();
        }
    }

    public Path getLocalStoragePath() {
        return localStoragePath;
    }
}