Class CompletableFutureExamples

java.lang.Object

net.jrodolfo.java_evolution.java08.CompletableFutureExamples

public class CompletableFutureExamples
extends Object

Demonstrates CompletableFuture, introduced in Java 8 to make asynchronous work easier to compose.

Before Java 8, Future could represent a result that would be available later, but it did not provide a fluent way to transform that result, combine it with another future, or recover from failure. Code often had to block with get() or coordinate callbacks manually.

CompletableFuture solves that problem by treating asynchronous work as a pipeline. A program can start work with supplyAsync, transform the result with thenApply, combine independent results with thenCombine, and handle errors with exceptionally. The examples use a caller-provided Executor so tests can run deterministically without depending on timing or background thread scheduling.

Constructor Summary

Constructors

Constructor	Description
CompletableFutureExamples(Executor executor)	Creates examples that run asynchronous stages on the supplied executor.

Method Summary

Modifier and Type	Method	Description
CompletableFuture<String>	fetchFullNameAsync()	Combines two independent futures with CompletableFuture.thenCombine(CompletionStage, BiFunction).
CompletableFuture<String>	fetchNameAsync()	Creates an asynchronous computation with CompletableFuture.supplyAsync(java.util.function.Supplier, Executor).
CompletableFuture<String>	fetchUppercaseNameAsync()	Chains a transformation with CompletableFuture.thenApply(Function).
String	fetchUppercaseNameBlocking()	Uses CompletableFuture.join() to wait for a composed future.
CompletableFuture<String>	recoverFromFailureAsync()	Recovers from a failed asynchronous computation with CompletableFuture.exceptionally(Function).

Methods inherited from class Object

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

Constructor Details

CompletableFutureExamples

public CompletableFutureExamples(Executor executor)

Creates examples that run asynchronous stages on the supplied executor.

Parameters:

executor - the executor used by asynchronous examples

Method Details

fetchNameAsync

public CompletableFuture<String> fetchNameAsync()

Creates an asynchronous computation with CompletableFuture.supplyAsync(java.util.function.Supplier, Executor).

Returns:

a future that eventually contains a name

fetchUppercaseNameAsync

public CompletableFuture<String> fetchUppercaseNameAsync()

Chains a transformation with CompletableFuture.thenApply(Function).

Returns:

a future containing the uppercase name

fetchFullNameAsync

public CompletableFuture<String> fetchFullNameAsync()

Combines two independent futures with CompletableFuture.thenCombine(CompletionStage, BiFunction).

Returns:

a future containing a full name

recoverFromFailureAsync

public CompletableFuture<String> recoverFromFailureAsync()

Recovers from a failed asynchronous computation with CompletableFuture.exceptionally(Function).

Returns:

a future containing a fallback value

fetchUppercaseNameBlocking

public String fetchUppercaseNameBlocking()

Uses CompletableFuture.join() to wait for a composed future.

Returns:

the uppercase name after the asynchronous pipeline completes