firebaseからデータの取り出しをしたい

前提・実現したいこと

android studio でマップアプリを作っています。
アプリでは、ユーザーに位置情報とその場所に関する情報を登録してもらうため、firebaseのrealtime databaseを用いてデータ管理をしています。
firebaseに登録されているデータを取り出し、マップ画面に表示をしたいのですが、そのデータの取り出しがうまくいきません。

発生している問題・エラーメッセージ

com.google.firebase.database.DatabaseException: Failed to convert value of type java.lang.Long to String

該当のソースコード

java
<Post.java>


public class Post {
    public String name;
    public String title;
    public String detail;
    public String image;
    public double latitude;
    public double longitude;
    public String comment;
    public String othercomment;
    public String userId;

    public Post(){

    }
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name=name;
    }
    public String getDetail(){
        return detail;
    }
    public void setDetail(String detail){
        this.detail=detail;
    }
    public String getTitle(){
        return title;
    }
    public void setTitle(String title){
        this.title=title;
    }
    public String getImage(){return image;}
    public void setImage(String image){
        this.image=image;
    }
    public double getLatitude(){return latitude;}
    public void setLatitude(double latitude){
        this.latitude=latitude;
    }
    public double getLongitude(){return longitude;}
    public void setLongitude(double longitude){
        this.longitude=longitude;
    }
    public String getComment(){return comment;}
    public void setComment(String comment){
        this.comment=comment;
    }
    /*public String getOtherComment(){return othercomment;}
    public void setOtherComment(String othercomment){
        this.othercomment=othercomment;
    }*/
    public String getuserId(){return userId;}
    public void setUserId(String userId){
        this.userId=userId;
    }
}

<MyMapActivity.java>

public class MyPostMapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;
    private int i=1;
    private long maxId;
    private double platitude;
    private double plongitude;
    private DatabaseReference reff,mImageDataref;
    private TextView tvmapTitle,tvmapDetail,tvmapComment,tvInfoOther;
    private ImageView ivMapCamera;
    private String commentList[],otherList[];
    private Marker markerList[];
    private String imageList[];
    Post post;
    String title;
    String detail;
    LatLng location;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_post_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
        tvmapTitle=findViewById(R.id.tvmapTitle);
        tvmapDetail=findViewById(R.id.tvmapDetail);
        tvmapComment=findViewById(R.id.tvmapComment);
        tvInfoOther=findViewById(R.id.tvInfoOther2);
        ivMapCamera=findViewById(R.id.ivMapCamera);
        Intent intent=getIntent();
        maxId=intent.getLongExtra("maxId",0);
      
    }

    public void setMarker(String title,String detail,LatLng location){
        mMap.setInfoWindowAdapter(new CustomInfoAdapter());
        MarkerOptions options=new MarkerOptions();
        options.position(location);
        options.title(title);
        options.snippet(detail);
        Marker marker=mMap.addMarker(options);
        markerList[i-1]=marker;
        marker.showInfoWindow();
    }

    private class CustomInfoAdapter implements GoogleMap.InfoWindowAdapter{
        private final View mWindow;
        public CustomInfoAdapter(){
            mWindow=getLayoutInflater().inflate(R.layout.info_window_layout,null);
        }

        @Override
        public View getInfoWindow(Marker marker){
            render(marker,mWindow);
            return mWindow;
        }
        @Override
        public View getInfoContents(Marker marker){
            return null;
        }

        private void render(Marker marker,View view){
            //省略
        }
    }

    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        LatLng present=new LatLng(platitude,plongitude);
        LatLng test=new LatLng(35.68944,139.69167);
        // Add a marker in Sydney and move the camera
        //mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(test,7));

        //データベース取得処理
        reff=FirebaseDatabase.getInstance().getReference("Post");
        reff.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull @NotNull DataSnapshot snapshot) {
                for(DataSnapshot data: snapshot.getChildren()){
                    post=data.getValue(Post.class);//エラー箇所
                    title=post.getTitle();
                    detail=post.getDetail();
                    //String image=post.getImage();
                    double latitude=post.getLatitude();
                    double longitude=post.getLongitude();
                    location=new LatLng(latitude,longitude);
                    String comment=post.getComment();
                    setMarker(title,detail,location);
                }
            }

            @Override
            public void onCancelled(@NonNull @NotNull DatabaseError error) {
                //データ取得失敗
                Toast.makeText(MyPostMapsActivity.this,"データ取得に失敗しました",Toast.LENGTH_SHORT).show();
            }
        });

        //Storageから画像取得処理
        mImageDataref =FirebaseDatabase.getInstance().getReference("uploads");
        mImageDataref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull @NotNull DataSnapshot snapshot) {
                for(DataSnapshot postSnapshot : snapshot.getChildren()){
                    Upload upload=postSnapshot.getValue(Upload.class);
                    //リストにuploadを入れる
                }
            }

            @Override
            public void onCancelled(@NonNull @NotNull DatabaseError error) {
                Toast.makeText(MyPostMapsActivity.this,"画像の取得に失敗しました",Toast.LENGTH_SHORT).show();
            }
        });


    }

    /*@Override
    public void onInfoWindowClick(Marker marker){
        //投稿編集画面へ移動
    }*/
}