:trollface:

hutool-core/src/main/java/cn/hutool/core/stream/CollectorUtil.java

@@ -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());
+	}
 }

hutool-core/src/test/java/cn/hutool/core/stream/CollectorUtilTest.java

@@ -47,7 +47,7 @@ public class CollectorUtilTest {
 
 	@Test
 	public void testToEasyStream() {
-		final Stream<Integer> stream =Stream.of(1, 2, 3, 4)
+		final Stream<Integer> stream = Stream.of(1, 2, 3, 4)
 				.collect(CollectorUtil.toEasyStream());
 		Assert.assertEquals(EasyStream.class, stream.getClass());
 	}
@@ -61,9 +61,21 @@ public class CollectorUtilTest {
 				.filterByKey(k -> (k & 1) == 1)
 				.inverse()
 				.toMap();
-		Assert.assertEquals((Integer)1, map.get("1"));
+		Assert.assertEquals((Integer) 1, map.get("1"));
-		Assert.assertEquals((Integer)3, map.get("3"));
+		Assert.assertEquals((Integer) 3, map.get("3"));
-		Assert.assertEquals((Integer)5, map.get("5"));
+		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);
+	}
 }