caching the result from a [n async] factory method iff it doesn't throw

caching the result from a [n async] factory method iff it doesn't throw

By : Robert Hess
Date : November 21 2020, 07:38 AM
I hope this helps . Does this get anywhere near your requirements?
The behaviour falls somewhere between ExecutionAndPublication and PublicationOnly.
code :
public sealed class TooLazy<T>
    private readonly object _lock = new object();
    private readonly Func<Task<T>> _factory;
    private Task<T> _cached;

    public TooLazy(Func<Task<T>> factory)
        if (factory == null) throw new ArgumentNullException("factory");
        _factory = factory;

    public Task<T> Value
            lock (_lock)
                if ((_cached == null) ||
                    (_cached.IsCompleted && (_cached.Status != TaskStatus.RanToCompletion)))
                    _cached = Task.Run(_factory);
                return _cached;

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What exception should I throw when a factory method returns null?

What exception should I throw when a factory method returns null?

By : Saravanakumar Muthus
Date : March 29 2020, 07:55 AM
help you fix your problem Consider a factory method that I may or may not control, passed to another class as a Func: , Two examples from the .NET Framework:
Java factory method caching

Java factory method caching

By : abhilash
Date : March 29 2020, 07:55 AM
To fix this issue If you don't mind using Guava, just:
Make CellPosition instances immutable, then Use an Interner (obtained from Interners), then Move on to solving real problems.
code :
class CellPosition
    private static final Interner<CellPosition> CACHE = Interners.newStrongInterner();
    // or .newWeakInterner(), to allow instances to be garbage collected

    private final int x;
    private final int y;

    private CellPosition(int x, int y)
        this.x = x;
        this.y = x;

    public int x() { return x; }
    public int y() { return y; }

    public static CellPosition at(int x, int y)
        return CACHE.intern(new CellPosition(x, y));

    public boolean equals(Object other) {/* TODO */}

    public int hashCode() {/* TODO */}
Why is my Observable 'caching' the result of an Async operation?

Why is my Observable 'caching' the result of an Async operation?

By : R-jay Miranda
Date : March 29 2020, 07:55 AM
hope this fix your issue I'm trying to listen for some connections using the standard System.Net Socket API and I'm planning on using Reactive Extensions to bridge the gap and create a intuitive way of listening to aforementioned connectionss. , By writing
code :
var task = Task.Factory.FromAsync(
    result => socket.EndAccept(result),
Func<Task<Socket>> acceptTask = () =>
    return Task.Factory.FromAsync(
        result => socket.EndAccept(result),
async.js : async.eachSeries result always throw undefined

async.js : async.eachSeries result always throw undefined

By : Ranjith Siva
Date : March 29 2020, 07:55 AM
Hope that helps The second argument is called when the iteration is done and with eachSeries(), it takes only one parameter, err. If you want result, you have to use mapSeries:
code :
async.mapSeries([1, 2, 3],
    function (data, cb) {
        setTimeout(function () {
            cb(null, data + 1);
        }, 1000);
    function (err, result) {
Why Java method doesnt throw exception in test class?

Why Java method doesnt throw exception in test class?

By : mrunal patel
Date : March 29 2020, 07:55 AM
Does that help A far more concise example works just fine. I disagree that test should inherit from Mammal, but left it in there for my example:
code :
public class Mammal {
int health =500;
  public void takeDamage(int damage) throws Exception{
    if(damage < 1) {
      throw new Exception("Damage cant be negative!");
    else this.health -= damage;
public class MTest extends Mammal {
public static void main(String args[]) {
    Mammal m = new Mammal();
    try {
    } catch(Exception e) {
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