DeclarativeX

A Composable approach to exception & conditions in Java

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Maven

        <dependency>
            <groupId>io.github.muthuishere</groupId>
            <artifactId>declarativex</artifactId>            
        </dependency>

Gradle

implementation "io.github.muthuishere:declarativex"

Usage

import declarativex.Try;
import declarativex.Filter;

Try

Instead of Writing This

List<String> results = null;

        try {
            results =newsService.downloadFromNyTimes(topic);
        }catch (Exception e){

            try {

                results =newsService.downloadFromHerald(topic);
            }catch (Exception e1){
                try {
                    results =newsService.downloadFromSun(topic);
                }catch (Exception e2){


                }
            }
        }

Write This

import declarativex.Try;

       results= Try.from(()->newsService.downloadFromNyTimes(topic))
                       .or(()->newsService.downloadFromHerald(topic))
                       .or(()->newsService.downloadFromSun(topic))
                       .get();

Or Even Better way

results= Try.any(newsService::downloadFromNyTimes,
                         newsService::downloadFromHerald,
                         newsService::downloadFromSun)
                        .with(topic)
                        .orElseGet(Arrays.asList("Some default"));

There are Additional Logging , Peek ,PeekError ,default value can convert to Optional as well

Also there is a lazy version of the same

results = Try.lazy.from(this::downloadCacheData)
                .get();

//Evaluation happens only after get is Invoked

Filter

Instead of Writing This

        if (age > 60) {
            result = "Can Retire";
        } else if (age > 40) {
            result = "Can Go World Tour";
        } else if (age > 32) {
            result = "Can Go for Job";
        } else if (age > 18) {
            result = "Can Go To College";
        } else {
            result = "Can Play";
        }

Write This

 result = Filter.If(() -> age > 60)
                .then("Can Retire")
                .elseIf(() -> age > 40)
                .then("Can Go World Tour")
                .elseIf(() -> age > 32)
                .then("Can Go for Job")
                .elseIf(() -> age > 18)
                .then("Can Go To College")
                .elseThen("Can Play")
                .get();