mirror of
https://github.com/tiennm99/java-design-patterns.git
synced 2026-05-19 09:26:25 +00:00
Ilkka Seppälä
932836f68b
* update license plugin * suppress linelength and emptylineseparator rules * fix checkstyle error Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>
85 lines
3.8 KiB
Java
85 lines
3.8 KiB
Java
/*
|
||
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
|
||
*
|
||
* The MIT License
|
||
* Copyright © 2014-2022 Ilkka Seppälä
|
||
*
|
||
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
||
* of this software and associated documentation files (the "Software"), to deal
|
||
* in the Software without restriction, including without limitation the rights
|
||
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
||
* copies of the Software, and to permit persons to whom the Software is
|
||
* furnished to do so, subject to the following conditions:
|
||
*
|
||
* The above copyright notice and this permission notice shall be included in
|
||
* all copies or substantial portions of the Software.
|
||
*
|
||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
||
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
||
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
||
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
||
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
||
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
||
* THE SOFTWARE.
|
||
*/
|
||
package com.iluwatar.dirtyflag;
|
||
|
||
import java.util.concurrent.Executors;
|
||
import java.util.concurrent.TimeUnit;
|
||
import lombok.extern.slf4j.Slf4j;
|
||
|
||
/**
|
||
* This application demonstrates the <b>Dirty Flag</b> pattern. The dirty flag behavioral pattern
|
||
* allows you to avoid expensive operations that would just need to be done again anyway. This is a
|
||
* simple pattern that really just explains how to add a bool value to your class that you can set
|
||
* anytime a property changes. This will let your class know that any results it may have previously
|
||
* calculated will need to be calculated again when they’re requested. Once the results are
|
||
* re-calculated, then the bool value can be cleared.
|
||
*
|
||
* <p>There are some points that need to be considered before diving into using this pattern:-
|
||
* there are some things you’ll need to consider:- (1) Do you need it? This design pattern works
|
||
* well when the results to be calculated are difficult or resource intensive to compute. You want
|
||
* to save them. You also don’t want to be calculating them several times in a row when only the
|
||
* last one counts. (2) When do you set the dirty flag? Make sure that you set the dirty flag within
|
||
* the class itself whenever an important property changes. This property should affect the result
|
||
* of the calculated result and by changing the property, that makes the last result invalid. (3)
|
||
* When do you clear the dirty flag? It might seem obvious that the dirty flag should be cleared
|
||
* whenever the result is calculated with up-to-date information but there are other times when you
|
||
* might want to clear the flag.
|
||
*
|
||
* <p>In this example, the {@link DataFetcher} holds the <i>dirty flag</i>. It fetches and
|
||
* re-fetches from <i>world.txt</i> when needed. {@link World} mainly serves the data to the
|
||
* front-end.
|
||
*/
|
||
@Slf4j
|
||
public class App {
|
||
|
||
/**
|
||
* Program execution point.
|
||
*/
|
||
public void run() {
|
||
final var executorService = Executors.newSingleThreadScheduledExecutor();
|
||
executorService.scheduleAtFixedRate(new Runnable() {
|
||
final World world = new World();
|
||
|
||
@Override
|
||
public void run() {
|
||
var countries = world.fetch();
|
||
LOGGER.info("Our world currently has the following countries:-");
|
||
countries.stream().map(country -> "\t" + country).forEach(LOGGER::info);
|
||
}
|
||
}, 0, 15, TimeUnit.SECONDS); // Run at every 15 seconds.
|
||
}
|
||
|
||
/**
|
||
* Program entry point.
|
||
*
|
||
* @param args command line args
|
||
*/
|
||
public static void main(String[] args) {
|
||
var app = new App();
|
||
app.run();
|
||
}
|
||
|
||
}
|