de.caff.generics

Class Late<T>

java.lang.Object

de.caff.generics.Late<T>

public class Late<T>
extends java.lang.Object

A lazy late loader task, which will load the value it represents in a background thread.

Background loading will start when some of the following three methods is called:

• get()

This class provides a part of the interface of Future, but does not allow for cancelling. The main reason is that cancelling is not perfectly well-defined here.

If you need to become informed that the loading has finished, forward this information from the value loader callable, possibly using something like SwingUtilities.invokeLater(Runnable).

Since:

June 12, 2025

Author:

Rammi

See Also:

Lazy

Constructor Summary

Constructors

Constructor and Description
Late(java.util.concurrent.ThreadPoolExecutor executor, java.util.concurrent.Callable<? extends T> valueLoader) Constructor.

Method Summary

Modifier and Type	Method and Description
void	dispose(java.lang.Runnable notYetLoadedHandler, java.util.function.Consumer<T> afterLoadHandler, java.util.function.Consumer<java.lang.Exception> errorHandler) Dispose the underlying value.
T	get() Get the value.
T	get(long timeout, java.util.concurrent.TimeUnit unit) Get the value, waiting for a given amount of time.
java.util.concurrent.ThreadPoolExecutor	getExecutor() Get the thread pool executor on which this task operates.
T	getOrDefault(T defaultValue) Get the already retrieved value, or a default if loading has not yet finished or has failed with an exception.
boolean	isDone() Is this task completed, either by retrieving the value or failing with an exception?
void	triggerLoad() Start loading the value if this has not already happened.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Late

public Late(@NotNull
            java.util.concurrent.ThreadPoolExecutor executor,
            @NotNull
            java.util.concurrent.Callable<? extends T> valueLoader)

Constructor.

Parameters:

executor - thread pool executor for handling value loads

valueLoader - loader for the value represented by this class

Method Detail

getExecutor

@NotNull
public java.util.concurrent.ThreadPoolExecutor getExecutor()

Get the thread pool executor on which this task operates.

Returns:

thread pool executor

isDone

public boolean isDone()

Is this task completed, either by retrieving the value or failing with an exception?

Returns:

true: this task is finished
false: this task has either never started or is not yet finished

getOrDefault

public T getOrDefault(T defaultValue)

Get the already retrieved value, or a default if loading has not yet finished or has failed with an exception.

Parameters:

defaultValue - default value

Returns:

the successfully retrieved value, or the default value if retrieving is unfinished or has failed

get

public T get()
      throws java.lang.InterruptedException,
             java.util.concurrent.ExecutionException

Get the value. If necessary, this method waits until the retrieving of the value has finished. See get(long, TimeUnit) for a way to not wait forever.

Returns:

the retrieved value

Throws:

java.lang.InterruptedException - if the retrieving task was interrupted

java.util.concurrent.ExecutionException - if the retrieving task failed with an exception

get

public T get(long timeout,
             @NotNull
             java.util.concurrent.TimeUnit unit)
      throws java.lang.InterruptedException,
             java.util.concurrent.ExecutionException,
             java.util.concurrent.TimeoutException

Get the value, waiting for a given amount of time. If necessary, this method waits until the retrieving of the value has finished, or the given time has passed. See get() for a way to wait forever.

Parameters:

timeout - waiting duration before this method ends in a TimeoutException

unit - time unit of the timeout

Returns:

the retrieved value

Throws:

java.lang.InterruptedException - if the retrieving task was interrupted

java.util.concurrent.ExecutionException - if the retrieving task failed with an exception

java.util.concurrent.TimeoutException - if retrieving took more time than allowed by the parameters

dispose

public void dispose(@NotNull
                    java.lang.Runnable notYetLoadedHandler,
                    @NotNull
                    java.util.function.Consumer<T> afterLoadHandler,
                    @NotNull
                    java.util.function.Consumer<java.lang.Exception> errorHandler)

Dispose the underlying value.

Parameters:

notYetLoadedHandler - called when the value was not yet loaded

afterLoadHandler - called when the value was successfully loaded

errorHandler - called when the loading of the value ran into an error

triggerLoad

public void triggerLoad()

Start loading the value if this has not already happened. This is sometimes useful if you plan a bulk read via get() from a single thread, which would effectively sequentialize the loading. Calling this method for all values together upfront will load in parallel.