Home / cs-notes / Language / Java / Concurrent / Code / Future / CompletableFuture / whenComplete

    public CompletableFuture<T> whenComplete(
        BiConsumer<? super T, ? super Throwable> action) {
        return uniWhenCompleteStage(null, action);
    }

    public CompletableFuture<T> whenCompleteAsync(
        BiConsumer<? super T, ? super Throwable> action) {
        return uniWhenCompleteStage(asyncPool, action);
    }

    public CompletableFuture<T> whenCompleteAsync(
        BiConsumer<? super T, ? super Throwable> action, Executor executor) {
        return uniWhenCompleteStage(screenExecutor(executor), action);
    }

    private CompletableFuture<T> uniWhenCompleteStage(
        Executor e, BiConsumer<? super T, ? super Throwable> f) {
        if (f == null) throw new NullPointerException();
        CompletableFuture<T> d = new CompletableFuture<T>();
        if (e != null || !d.uniWhenComplete(this, f, null)) {
            UniWhenComplete<T> c = new UniWhenComplete<T>(e, d, this, f);
            push(c);
            c.tryFire(SYNC);
        }
        return d;
    }

    @SuppressWarnings("serial")
    static final class UniWhenComplete<T> extends UniCompletion<T,T> {
        BiConsumer<? super T, ? super Throwable> fn;
        UniWhenComplete(Executor executor, CompletableFuture<T> dep,
                        CompletableFuture<T> src,
                        BiConsumer<? super T, ? super Throwable> fn) {
            super(executor, dep, src); this.fn = fn;
        }
        final CompletableFuture<T> tryFire(int mode) {
            CompletableFuture<T> d; CompletableFuture<T> a;
            if ((d = dep) == null ||
                !d.uniWhenComplete(a = src, fn, mode > 0 ? null : this))
                return null;
            dep = null; src = null; fn = null;
            return d.postFire(a, mode);
        }
    }

    final boolean uniWhenComplete(CompletableFuture<T> a,
                                  BiConsumer<? super T,? super Throwable> f,
                                  UniWhenComplete<T> c) {
        Object r; T t; Throwable x = null;
        if (a == null || (r = a.result) == null || f == null)
            return false;
        if (result == null) {
            try {
                if (c != null && !c.claim())
                    return false;
                if (r instanceof AltResult) {
                    x = ((AltResult)r).ex;
                    t = null;
                } else {
                    @SuppressWarnings("unchecked") T tr = (T) r;
                    t = tr;
                }
                f.accept(t, x);
                if (x == null) {
                    internalComplete(r);
                    return true;
                }
            } catch (Throwable ex) {
                if (x == null)
                    x = ex;
            }
            completeThrowable(x, r);
        }
        return true;
    }

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