feat: Join支持key为null的情况

Author: lokic

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.github.lokic</groupId>
     <artifactId>java-plus</artifactId>
-    <version>0.1.0</version>
+    <version>0.1.1</version>
     <name>java-plus</name>
     <description>Provide some useful extensions on the basis of java8 to make java more usable.</description>
     <url>https://github.com/lokic/java-plus</url>

src/main/java/com/github/lokic/javaplus/Join.java

@@ -3,10 +3,7 @@
 import com.github.lokic.javaplus.tuple.Tuple;
 import com.github.lokic.javaplus.tuple.Tuple2;
 
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Map;
-import java.util.Objects;
+import java.util.*;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Collector;
@@ -71,15 +68,25 @@ public static class JoinType<T1, T2> {
         private final Stream<Tuple2<T1, T2>> rightWrappedStream;
         private final Predicate<Tuple2<T1, T2>> joinMatcher;
 
-        public JoinType(Stream<T1> left, Stream<T2> right, Predicate<Tuple2<T1, T2>> joinMatcher) {
+        private JoinType(Stream<T1> left, Stream<T2> right, Predicate<Tuple2<T1, T2>> joinMatcher) {
             this.leftWrappedStream = left.map(l -> Tuple.of(Objects.requireNonNull(l), null));
             this.rightWrappedStream = right.map(r -> Tuple.of(null, Objects.requireNonNull(r)));
             this.joinMatcher = joinMatcher;
         }
 
         public <K> JoinStream<T1, T2> on(Function<T1, K> leftKey, Function<T2, K> rightKey) {
             Stream<Tuple2<T1, T2>> stream = Stream.concat(leftWrappedStream, rightWrappedStream)
-                    .collect(Collectors.groupingBy(t -> matchKey(t, leftKey, rightKey)))
+                    .collect(Collectors.toMap(
+                            t -> matchKey(t, leftKey, rightKey),
+                            Collections::singletonList,
+                            (a, b) -> {
+                                List<Tuple2<T1, T2>> li = new ArrayList<>();
+                                li.addAll(a);
+                                li.addAll(b);
+                                return li;
+                            },
+                            LinkedHashMap::new
+                    ))
                     .values()
                     .stream()
                     .flatMap(this::cartesian)

src/test/java/com/github/lokic/javaplus/JoinTest.java

@@ -106,4 +106,29 @@ public void test_joinStream_leftOuterJoin() {
                         Tuple.of(3, "3", null),
                         Tuple.of(4, null, null));
     }
+
+    @Test
+    public void test_nullKey() {
+        List<Tuple2<Integer, Integer>> list = Join.leftOuterJoin(Stream.of(new KeyBox(1), new KeyBox(2), new KeyBox(3), new KeyBox(4), new KeyBox(null)), Stream.of(2, 3, 5))
+                .on(KeyBox::getKey, Function.identity())
+                .stream()
+                .map(t -> Tuple.of(t.getT1().getKey(), t.getT2()))
+                .collect(Collectors.toList());
+        Assertions.assertThat(list)
+                .containsExactly(Tuple.of(1, null), Tuple.of(2, 2), Tuple.of(3, 3),
+                        Tuple.of(4, null), Tuple.of(null, null));
+
+    }
+
+    public static class KeyBox {
+        private final Integer key;
+
+        public KeyBox(Integer key) {
+            this.key = key;
+        }
+
+        public Integer getKey() {
+            return key;
+        }
+    }
 }