Introducing the core-java-12 module.

It's ignored just like other 9+ versions.

core-java-12/src/test/java/com/baeldung/collectors/CollectorsUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.collectors;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+import org.junit.Test;
+
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.minBy;
+import static java.util.stream.Collectors.teeing;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for collectors additions in Java 12.
+ */
+public class CollectorsUnitTest {
+
+	@Test
+	public void whenTeeing_ItShouldCombineTheResultsAsExpected() {
+		List<Integer> numbers = Arrays.asList(42, 4, 2, 24);
+		Range range = numbers.stream()
+				.collect(teeing(
+						minBy(Integer::compareTo),
+						maxBy(Integer::compareTo),
+						(min, max) -> new Range(min.orElse(null), max.orElse(null))
+				));
+
+		assertThat(range).isEqualTo(new Range(2, 42));
+	}
+
+	/**
+	 * Represents a closed range of numbers between {@link #min} and
+	 * {@link #max}, both inclusive.
+	 */
+	private static class Range {
+
+		private final Integer min;
+
+		private final Integer max;
+
+		Range(Integer min, Integer max) {
+			this.min = min;
+			this.max = max;
+		}
+
+		Integer getMin() {
+			return min;
+		}
+
+		Integer getMax() {
+			return max;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o) return true;
+			if (o == null || getClass() != o.getClass()) return false;
+			Range range = (Range) o;
+			return Objects.equals(getMin(), range.getMin()) &&
+					Objects.equals(getMax(), range.getMax());
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(getMin(), getMax());
+		}
+
+		@Override
+		public String toString() {
+			return "Range{" +
+					"min=" + min +
+					", max=" + max +
+					'}';
+		}
+	}
+}