Asked  7 Months ago    Answers:  5   Viewed   70 times

I saw this list of major version numbers for Java in another post:

  • Java 1.2 uses major version 46
  • Java 1.3 uses major version 47
  • Java 1.4 uses major version 48
  • Java 5 uses major version 49
  • Java 6 uses major version 50
  • Java 7 uses major version 51
  • Java 8 uses major version 52
  • Java 9 uses major version 53
  • Java 10 uses major version 54
  • Java 11 uses major version 55
  • Java 12 uses major version 56
  • Java 13 uses major version 57
  • Java 14 uses major version 58
  • Java 15 uses major version 59
  • Java 16 uses major version 60

Where does this list come from? Is there a specific reference for this? Preferably something that shows minor versions too?



These come from the class version. If you try to load something compiled for java 6 in a java 5 runtime you'll get the error, incompatible class version, got 50, expected 49. Or something like that.

See here in byte offset 7 for more info.

Additional info can also be found here.

Tuesday, June 1, 2021
answered 7 Months ago

You have essentially compiled your code with JDK 1.6 but running it with Java 5 - Just ensure a Java 6 runtime.

Friday, July 30, 2021
Sam Adamsh
answered 5 Months ago

The @version tag should be the current version of the release or file in question. The %I%, %G% syntax are macros that the source control software would replace with the current version of the file and the date when the file is checked out.

The @since tag should be used to define which version you added the method, class, etc. This is your hint to other developers that they should only expect the method when they run against a particular version of the package. I would consider these uber-important parts of the documentation if you're shipping your code as a library intended for someone else to use.

Sunday, August 1, 2021
answered 5 Months ago

These classes are created from anonymous classes created in your applet - most likely event listeners and such.

They would be created (maybe with other names) by other compilers, too.

If you really want to avoid them, program without anonymous (and other inner) classes. But this results often in an ugly style, so this is not recommended.

If you don't want to upload all the individual class files to the server (and then the browsers having to fetch them all individually), think about putting them all in one jar file, and referencing this in your applet-tag.

Monday, August 30, 2021
answered 4 Months ago

There's no need for a JavaFX-specific executor service: the regular java.util.concurrent.ExecutorService works just fine, as Task is a subclass of FutureTask.

Once you have a list of tasks, you can compute the overall progress as a function of the progress of each of them. For example, it might just be the sum of the progress of all, divided by the number of tasks. If each task has a different number of items to process, you might be able to do something more sophisticated.

Here's a simple SSCCE:

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import javafx.application.Application;
import javafx.beans.binding.DoubleBinding;
import javafx.concurrent.Task;
import javafx.concurrent.Worker;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.control.TextArea;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class MultipleTaskTest extends Application {

    private final ExecutorService exec = Executors.newFixedThreadPool(5, r -> {
        Thread t = new Thread(r);
        return t ;

    private final Random rng = new Random();

    public void start(Stage primaryStage) {

        Label pendingTasksLabel = new Label();
        Button button = new Button("Launch tasks");
        TextArea log = new TextArea();

        DoubleProperty progress = new SimpleDoubleProperty(1);

        ProgressBar progressBar = new ProgressBar();

        IntegerProperty pendingTasks = new SimpleIntegerProperty(0);
        pendingTasksLabel.textProperty().bind(pendingTasks.asString("Pending Tasks: %d"));


        button.setOnAction(e -> {
            int numTasks = rng.nextInt(5) + 4 ;

            List<Task<Void>> tasks = new ArrayList<>();
            for (int i = 0; i < numTasks; i++) {

            // rebind progress:
            progress.bind( new DoubleBinding() {
                    for (Task<Void> task : tasks) {

                public double computeValue() {
                        task -> Math.max(task.getProgress(), 0)    
                    )) / numTasks;

            log.appendText("Submitting "+numTasks+" tasksn");


            // log state of each task:
            tasks.forEach(task -> 
                task.stateProperty().addListener((obs, oldState, newState) -> {
                    log.appendText("tTask "+newState+"n");

                    // update pendingTasks if task moves out of running state:                  
                    if (oldState == Worker.State.RUNNING) {
                        pendingTasks.set(pendingTasks.get() - 1);


        VBox root = new VBox(10, pendingTasksLabel, progressBar, log, button);
        root.setPadding(new Insets(10));
        VBox.setVgrow(log, Priority.ALWAYS);

        primaryStage.setScene(new Scene(root, 400, 400));;

    public void stop() {
        exec.shutdownNow() ;

    private Task<Void> createRandomTask() {
        int numSteps = 100 + rng.nextInt(100);
        return new Task<Void>() {
            public Void call() throws Exception {
                for (int i = 1; i <= numSteps; i++) {
                    updateProgress(i, numSteps);
                return null ;

    public static void main(String[] args) {
Tuesday, November 9, 2021
answered 1 Month ago
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