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* Implement concatenation * Fix doc error * Renamed `thenConcat` to `concat`
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src/main/java/com/ginsberg/gatherers4j/ConcatenationGatherer.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,68 @@ | ||
| /* | ||
| * Copyright 2024 Todd Ginsberg | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| package com.ginsberg.gatherers4j; | ||
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| import java.util.ArrayList; | ||
| import java.util.List; | ||
| import java.util.function.BiConsumer; | ||
| import java.util.function.Supplier; | ||
| import java.util.stream.Gatherer; | ||
| import java.util.stream.Stream; | ||
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| import static com.ginsberg.gatherers4j.GathererUtils.mustNotBeNull; | ||
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| public class ConcatenationGatherer<INPUT> implements Gatherer<INPUT, ConcatenationGatherer.State<INPUT>, INPUT> { | ||
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| private final List<Stream<INPUT>> concatThese = new ArrayList<>(); | ||
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| ConcatenationGatherer(final Stream<INPUT> concatThis) { | ||
| concat(concatThis); | ||
| } | ||
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| public final ConcatenationGatherer<INPUT> concat(final Stream<INPUT> concatThis) { | ||
| mustNotBeNull(concatThis, "Concatenated stream must not be null"); | ||
| this.concatThese.add(concatThis); | ||
| return this; | ||
| } | ||
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| @Override | ||
| public Supplier<State<INPUT>> initializer() { | ||
| return () -> new State<>(concatThese); | ||
| } | ||
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| @Override | ||
| public Integrator<State<INPUT>, INPUT, INPUT> integrator() { | ||
| return (_, element, downstream) -> downstream.push(element); | ||
| } | ||
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| @Override | ||
| public BiConsumer<State<INPUT>, Downstream<? super INPUT>> finisher() { | ||
| return (state, downstream) -> { | ||
| for (Stream<INPUT> concatThis : state.concatThese) { | ||
| concatThis.forEach(downstream::push); | ||
| } | ||
| }; | ||
| } | ||
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| public static class State<INPUT> { | ||
| final List<Stream<INPUT>> concatThese; | ||
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| public State(List<Stream<INPUT>> concatThese) { | ||
| this.concatThese = concatThese; | ||
| } | ||
| } | ||
| } |
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src/test/java/com/ginsberg/gatherers4j/ConcatenationGathererTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| /* | ||
| * Copyright 2024 Todd Ginsberg | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
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| package com.ginsberg.gatherers4j; | ||
|
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| import org.junit.jupiter.api.Test; | ||
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| import java.util.List; | ||
| import java.util.stream.Stream; | ||
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| import static org.assertj.core.api.Assertions.assertThat; | ||
| import static org.assertj.core.api.Assertions.assertThatThrownBy; | ||
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| class ConcatenationGathererTest { | ||
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| @Test | ||
| void additionalStreamCannotBeNull() { | ||
| assertThatThrownBy(() -> | ||
| Stream.of("A").gather(Gatherers4j.concat(Stream.of("1")).concat(null)) | ||
| ).isExactlyInstanceOf(IllegalArgumentException.class); | ||
| } | ||
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| @Test | ||
| void allowsEmptyConcat() { | ||
| // Arrange | ||
| final Stream<String> input1 = Stream.of("A", "B", "C"); | ||
| final Stream<String> input2 = Stream.empty(); | ||
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| // Act | ||
| final List<String> output = input1.gather(Gatherers4j.concat(input2)).toList(); | ||
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| // Assert | ||
| assertThat(output).containsExactly("A", "B", "C"); | ||
| } | ||
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| @Test | ||
| void allowsEmptySource() { | ||
| // Arrange | ||
| final Stream<String> input1 = Stream.empty(); | ||
| final Stream<String> input2 = Stream.of("D", "E", "F"); | ||
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| // Act | ||
| final List<String> output = input1.gather(Gatherers4j.concat(input2)).toList(); | ||
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| // Assert | ||
| assertThat(output).containsExactly("D", "E", "F"); | ||
| } | ||
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| @Test | ||
| void initialStreamCannotBeNull() { | ||
| assertThatThrownBy(() -> | ||
| Stream.of("A").gather(Gatherers4j.concat(null)) | ||
| ).isExactlyInstanceOf(IllegalArgumentException.class); | ||
| } | ||
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| @Test | ||
| void multipleConcatenations() { | ||
| // Arrange | ||
| final Stream<String> input1 = Stream.of("A", "B", "C"); | ||
| final Stream<String> input2 = Stream.of("D", "E", "F"); | ||
| final Stream<String> input3 = Stream.of("G", "H", "I"); | ||
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| // Act | ||
| final List<String> output = input1.gather(Gatherers4j.concat(input2).concat(input3)).toList(); | ||
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| // Assert | ||
| assertThat(output).containsExactly("A", "B", "C", "D", "E", "F", "G", "H", "I"); | ||
| } | ||
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| @Test | ||
| void simpleConcatenation() { | ||
| // Arrange | ||
| final Stream<String> input1 = Stream.of("A", "B", "C"); | ||
| final Stream<String> input2 = Stream.of("D", "E", "F"); | ||
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| // Act | ||
| final List<String> output = input1.gather(Gatherers4j.concat(input2)).toList(); | ||
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| // Assert | ||
| assertThat(output).containsExactly("A", "B", "C", "D", "E", "F"); | ||
| } | ||
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| } |