streams/src/main/java/org/apache/kafka/streams/kstream/internals/SlidingWindowedKStreamImpl.java [101:141]:
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                materializedInternal.valueSerde());
    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator) {
        return aggregate(initializer, aggregator, Materialized.with(keySerde, null));
    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator,
                                                  final Named named) {
        return aggregate(initializer, aggregator, named, Materialized.with(keySerde, null));
    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator,
                                                  final Materialized<K, VR, WindowStore<Bytes, byte[]>> materialized) {
        return aggregate(initializer, aggregator, NamedInternal.empty(), materialized);
    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator,
                                                  final Named named,
                                                  final Materialized<K, VR, WindowStore<Bytes, byte[]>> materialized) {
        Objects.requireNonNull(initializer, "initializer can't be null");
        Objects.requireNonNull(aggregator, "aggregator can't be null");
        Objects.requireNonNull(materialized, "materialized can't be null");
        final MaterializedInternal<K, VR, WindowStore<Bytes, byte[]>> materializedInternal =
                new MaterializedInternal<>(materialized, builder, AGGREGATE_NAME);
        if (materializedInternal.keySerde() == null) {
            materializedInternal.withKeySerde(keySerde);
        }
        final String aggregateName = new NamedInternal(named).orElseGenerateWithPrefix(builder, AGGREGATE_NAME);

        return aggregateBuilder.build(
                new NamedInternal(aggregateName),
                materialize(materializedInternal),
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streams/src/main/java/org/apache/kafka/streams/kstream/internals/TimeWindowedKStreamImpl.java [114:158]:
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                materializedInternal.valueSerde());


    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator) {
        return aggregate(initializer, aggregator, Materialized.with(keySerde, null));
    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator,
                                                  final Named named) {
        return aggregate(initializer, aggregator, named, Materialized.with(keySerde, null));
    }


    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator,
                                                  final Materialized<K, VR, WindowStore<Bytes, byte[]>> materialized) {
        return aggregate(initializer, aggregator, NamedInternal.empty(), materialized);
    }

    @Override
    public <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                                  final Aggregator<? super K, ? super V, VR> aggregator,
                                                  final Named named,
                                                  final Materialized<K, VR, WindowStore<Bytes, byte[]>> materialized) {
        Objects.requireNonNull(initializer, "initializer can't be null");
        Objects.requireNonNull(aggregator, "aggregator can't be null");
        Objects.requireNonNull(materialized, "materialized can't be null");
        final MaterializedInternal<K, VR, WindowStore<Bytes, byte[]>> materializedInternal =
            new MaterializedInternal<>(materialized, builder, AGGREGATE_NAME);
        if (materializedInternal.keySerde() == null) {
            materializedInternal.withKeySerde(keySerde);
        }

        final String aggregateName = new NamedInternal(named).orElseGenerateWithPrefix(builder, AGGREGATE_NAME);

        return aggregateBuilder.build(
                new NamedInternal(aggregateName),
                materialize(materializedInternal),
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