Cancelling method calls when the same method is called multiple time

Question

I think there\'s probably a name for what I\'m describing here, but I don\'t know it. So my first question would be to know the name of this technique.

Here\'s an ex

Answer 1

This is not solvable in Java without using some extra infrastructure like you did with executor and futures. It is not possible to solve this in syntactically concise manner in Java.

You will always need some sort of method result wrapper, because the mechanism returns immediately but the actual result is retrieved later. In your case this was accomplished via Future.

You will always need to be able to specify code to be executed in a manner that will allow delayed execution. In most languages this is accomplished using function pointers or function values or closures. In Java, lacking these language features, this is usually accomplished by passing an object that implements some sort of interface such as Runnable, Callable, that allows delayed execution of a block of code. There are other options but none of them are simple, such as using a dynamic proxy.

tl;dr

Can't do this in concise manner in Java.

Answer 2

What you need is called debouncing. You should check the jQuery Throttle/Debounce plugin (which is btw totally independent of jQuery except for using the same namespace). What you need is covered by the debounce part:

Using jQuery throttle / debounce, you can pass a delay and function to $.debounce to get a new function, that when called repetitively, executes the original function just once per “bunch” of calls, effectively coalescing multiple sequential calls into a single execution at either the beginning or end.

Underscore.js has the same method:

_.debounce(function, wait, [immediate]) 

Creates and returns a new debounced version of the passed function which will postpone its execution until after wait milliseconds have elapsed since the last time it was invoked. Useful for implementing behavior that should only happen after the input has stopped arriving. For example: rendering a preview of a Markdown comment, recalculating a layout after the window has stopped being resized, and so on.

// example: debounce layout calculation on window resize
var lazyLayout = _.debounce(calculateLayout, 300);
$(window).resize(lazyLayout);

[Edit]

I mistakenly read "Javascript" instead of Java. Actual Java solution was written by OP afterwards.

Answer 3

Given the other answers, and after some searching, it seems there's indeed no library that does what I wanted.

I created one and put it on GitHub. Future readers of this question may find it interesting.

https://github.com/ThomasGirard/JDebounce

I don't think it's very good yet but at least it works and can be used declaratively:

@Debounce(delayMilliseconds = 100)
public void debouncedMethod(int callID, DebounceTest callback) { }