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TanShengyuan 2022-09-24 17:07:56 +08:00 committed by Rosie
parent 62c80a2184
commit 0f3c658746
2 changed files with 53 additions and 20 deletions
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21
hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java
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@ -495,4 +495,25 @@ public class CollectorUtil {
};
}
/**
* <p>过滤</p >
*
* @param predicate 断言
* @param downstream 下游操作
* @param <T> 元素类型
* @param <A> 中间类型
* @param <R> 结束类型
* @return 一个用于过滤元素的 {@link java.util.stream.Collector}
* @author TanShengYuan
*/
public static <T, A, R>
Collector<T, ?, R> filtering(final Predicate<? super T> predicate,
final Collector<? super T, A, R> downstream) {
final BiConsumer<A, ? super T> downstreamAccumulator = downstream.accumulator();
return new SimpleCollector<>(downstream.supplier(),
(r, t) -> Opt.of(t).filter(predicate).ifPresent(e -> downstreamAccumulator.accept(r, e)),
downstream.combiner(), downstream.finisher(),
downstream.characteristics());
}
}

52
hutool-core/src/test/java/cn/hutool/core/stream/CollectorUtilTest.java
View File

@ -20,50 +20,62 @@ public class CollectorUtilTest {
@Test
public void reduceListMapTest() {
final Set<Map<String, Integer>> nameScoreMapList = StreamUtil.of(
// 集合内的第一个map，包含两个key value
MapUtil.builder("苏格拉底", 1).put("特拉叙马霍斯", 3).build(),
MapUtil.of("苏格拉底", 2),
MapUtil.of("特拉叙马霍斯", 1),
MapUtil.of("特拉叙马霍斯", 2)
// 集合内的第一个map，包含两个key value
MapUtil.builder("苏格拉底", 1).put("特拉叙马霍斯", 3).build(),
MapUtil.of("苏格拉底", 2),
MapUtil.of("特拉叙马霍斯", 1),
MapUtil.of("特拉叙马霍斯", 2)
).collect(Collectors.toSet());
// 执行聚合
final Map<String, List<Integer>> nameScoresMap = nameScoreMapList.stream().collect(CollectorUtil.reduceListMap());
Assert.assertEquals(MapUtil.builder("苏格拉底", Arrays.asList(1, 2))
.put("特拉叙马霍斯", Arrays.asList(3, 1, 2)).build(),
nameScoresMap);
.put("特拉叙马霍斯", Arrays.asList(3, 1, 2)).build(),
nameScoresMap);
}
@Test
public void testTransform() {
Stream<Integer> stream = Stream.of(1, 2, 3, 4)
.collect(CollectorUtil.transform(EasyStream::of));
.collect(CollectorUtil.transform(EasyStream::of));
Assert.assertEquals(EasyStream.class, stream.getClass());
stream = Stream.of(1, 2, 3, 4)
.collect(CollectorUtil.transform(HashSet::new, EasyStream::of));
.collect(CollectorUtil.transform(HashSet::new, EasyStream::of));
Assert.assertEquals(EasyStream.class, stream.getClass());
}
@Test
public void testToEasyStream() {
final Stream<Integer> stream =Stream.of(1, 2, 3, 4)
.collect(CollectorUtil.toEasyStream());
final Stream<Integer> stream = Stream.of(1, 2, 3, 4)
.collect(CollectorUtil.toEasyStream());
Assert.assertEquals(EasyStream.class, stream.getClass());
}
@Test
public void testToEntryStream() {
final Map<String, Integer> map = Stream.of(1, 2, 3, 4, 5)
// 转为EntryStream
.collect(CollectorUtil.toEntryStream(Function.identity(), String::valueOf))
// 过滤偶数
.filterByKey(k -> (k & 1) == 1)
.inverse()
.toMap();
Assert.assertEquals((Integer)1, map.get("1"));
Assert.assertEquals((Integer)3, map.get("3"));
Assert.assertEquals((Integer)5, map.get("5"));
// 转为EntryStream
.collect(CollectorUtil.toEntryStream(Function.identity(), String::valueOf))
// 过滤偶数
.filterByKey(k -> (k & 1) == 1)
.inverse()
.toMap();
Assert.assertEquals((Integer) 1, map.get("1"));
Assert.assertEquals((Integer) 3, map.get("3"));
Assert.assertEquals((Integer) 5, map.get("5"));
}
@Test
public void testFiltering() {
final Map<Integer, Long> map = Stream.of(1, 2, 3)
.collect(Collectors.groupingBy(Function.identity(),
CollectorUtil.filtering(i -> i > 1, Collectors.counting())
));
Assert.assertEquals(MapUtil.builder()
.put(1, 0L)
.put(2, 1L)
.put(3, 1L)
.build(), map);
}
}