JavaFX memory leak in TableView with dynamic TableColumns - memory-leaks

Question

I am using jdk1.8.0_40
I want to make a TableView which can have dynamically changing columns, but it leaks memory in Old/Tenured gen and eventually hangs the JVM.
Here is a simple program that demonstrates the leak (imports not included):
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
TableView<ObservableList<String>> tableView = new TableView<>();
Button button = new Button("button");
button.setOnAction((actionEvent) -> {
// Clearing items and/or columns here doesn't remove the leak
tableView.getItems().clear();
tableView.getColumns().clear();
for (int g = 0; g < 50; g++) { // iterate 50 times to see the leak quickly
TableColumn<ObservableList<String>, String> tableColumn = new TableColumn<>("column");
tableView.getColumns().add(tableColumn);
}
tableView.getItems().add(FXCollections.observableArrayList("1"));
// clearing the items here removes the leak somehow, but also makes the table useless
/* tableView.getItems().clear(); */
});
primaryStage.setScene(new Scene(new VBox(tableView, button), 800, 600));
primaryStage.show();
}
public static void main(String[] args) { launch(args); }
}
In the code above pressing the button 2nd time should clear all items and columns, and it does, but some reference somehow persists somewhere.
Some things I've already tried:
Tried searching for similar issues, but didn't find anything relevant.
Tried storing all the references in an ArrayList and explicitly remove()-ing them instead of clear() - didn't work.
Tried using ListView, which works fine, but it isn't a table and can't have columns.
Tried using different combinations of classes (e.g. StringProperty instead of String), which to no surprise also didn't work.
I have only recently started learning JavaFX so I may just be missing something obvious, if so - sorry for a dumb question.
How do I fix this leak?
If it can't be fixed, is it a bug, or is this intended behavior and I should not create TableColumn dynamically?

Answer 1

To answer my own question in case somebody is also having this issue - this is a bug.
I submitted a JIRA bug report, for more info and maybe updates see https://javafx-jira.kenai.com/browse/RT-40325

Answer 2

If you suspect that there's a leak, you fix it by first identifying it using a profiler.
I rewrote your sample (which wasn't showing any data btw), there doesn't seem to be a leak. Try this and check the console output.
import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class MainLeak extends Application {
private static final int iterations = 100;
private static final int columns = 50;
private static final int rows = 100;
#Override
public void start(Stage primaryStage) {
TableView<ObservableList<StringProperty>> table = new TableView<>();
Button button = new Button("button");
button.setOnAction((actionEvent) -> {
addData( table, iterations);
});
addData( table, iterations);
primaryStage.setScene(new Scene(new VBox(table, button), 800, 600));
primaryStage.show();
}
private void addData( TableView table, int iterations) {
for (int i = 0; i < iterations; i++) {
final int index = i;
addData(table);
System.gc();
System.out.println(index + ": free: " + Runtime.getRuntime().freeMemory() / 1024 + " kb, max: " + Runtime.getRuntime().maxMemory() / 1024 + " kb");
}
}
private void addData(TableView table) {
table.getItems().clear();
table.getColumns().clear();
for( int col=0; col < columns; col++) {
table.getColumns().add(createColumn(col));
}
for( int row=0; row < rows; row++) {
ObservableList<StringProperty> data = FXCollections.observableArrayList();
for( int col=0; col < columns; col++) {
data.add(new SimpleStringProperty(String.valueOf( row + " / " + col)));
}
table.getItems().add(data);
}
}
private TableColumn<ObservableList<StringProperty>, String> createColumn(final int columnIndex) {
TableColumn<ObservableList<StringProperty>, String> column = new TableColumn<>();
String title = "Column " + columnIndex;
column.setText(title);
column.setCellValueFactory(cellDataFeatures -> cellDataFeatures.getValue().get(columnIndex));
return column;
}
public static void main(String[] args) {
launch(args);
}
}