Java SE 21 Developer
Master the latest Java 21 features and core programming paradigms with the official Oracle Java SE 21 Developer Professional certification to validate your expert-level software engineering capabilities.
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Try a real question
Sample Java SE 21 Developer exam question
Answer this question the same way you would on exam day. No sign-up needed — one random question, three tries to swap it out.
Examine the completable-future chain shown in the code block. Suppose the first stage succeeds and then the thenApply lambda throws a new IllegalStateException. What is the printed result?
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;
CompletableFuture<String> stage =
CompletableFuture.supplyAsync(() -> "ok")
.exceptionally(e -> "fallback")
.thenApply(v -> { throw new IllegalStateException("late failure"); });
try {
System.out.println(stage.join());
} catch (CompletionException ex) {
System.out.println(ex.getCause().getClass().getSimpleName());
}Frequently asked questions
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