Both<> collectors

Author: fluentfuture

mug-guava/src/main/java/com/google/mu/util/stream/GuavaCollectors.java

@@ -14,6 +14,7 @@
  *****************************************************************************/
 package com.google.mu.util.stream;
 
+import static com.google.mu.util.stream.MoreStreams.mapping;
 import static java.util.Objects.requireNonNull;
 import static java.util.function.Function.identity;
 
@@ -35,6 +36,7 @@
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Multimaps;
 import com.google.common.collect.Tables;
+import com.google.mu.util.Both;
 
 /**
  * Guava-specific Collectors and BiCollectors.
@@ -232,7 +234,7 @@ public static <K, V> BiCollector<K, V, ImmutableMultiset<K>> toImmutableMultiset
    * Returns a {@link BiCollector} that collects the key-value pairs into an {@link ImmutableBimap}.
    * Equivalent to {@code ImmutableBimap::toImmutableBimap}.
    */
-  public static <K, V> BiCollector<K, V, ImmutableBiMap<K, V>> toImmutableBimap() {
+  public static <K, V> BiCollector<K, V, ImmutableBiMap<K, V>> toImmutableBiMap() {
     return ImmutableBiMap::toImmutableBiMap;
   }
 
@@ -283,6 +285,49 @@ public static <K, V> BiCollector<K, V, ImmutableBiMap<K, V>> toImmutableBimap()
             (builder, that) -> builder.putAll(that.build()),
             ImmutableTable.Builder::build));
   }
+  /**
+   * Returns a collector that first maps each input into a key-value pair, and then collects them
+   * into a {@link ImmutableMap}.
+   *
+   * @since 5.1
+   */
+  public static <T, K, V> Collector<T, ?, ImmutableMap<K, V>> toImmutableMap(
+      Function<? super T, ? extends Both<? extends K, ? extends V>> mapper) {
+    return mapping(mapper, toImmutableMap());
+  }
+
+  /**
+   * Returns a collector that first maps each input into a key-value pair, and then collects them
+   * into a {@link ImmutableListMultimap}.
+   *
+   * @since 5.1
+   */
+  public static <T, K, V> Collector<T, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap(
+      Function<? super T, ? extends Both<? extends K, ? extends V>> mapper) {
+    return mapping(mapper, toImmutableListMultimap());
+  }
+
+  /**
+   * Returns a collector that first maps each input into a key-value pair, and then collects them
+   * into a {@link ImmutableSetMultimap}.
+   *
+   * @since 5.1
+   */
+  public static <T, K, V> Collector<T, ?, ImmutableSetMultimap<K, V>> toImmutableSetMultimap(
+      Function<? super T, ? extends Both<? extends K, ? extends V>> mapper) {
+    return mapping(mapper, toImmutableSetMultimap());
+  }
+
+  /**
+   * Returns a collector that first maps each input into a key-value pair, and then collects them
+   * into a {@link ImmutableBiMap}.
+   *
+   * @since 5.1
+   */
+  public static <T, K, V> Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
+      Function<? super T, ? extends Both<? extends K, ? extends V>> mapper) {
+    return mapping(mapper, toImmutableBiMap());
+  }
 
   private static <K, V, T, R> BiCollector<K, V, R> mappingValues(
       Function<? super V, ? extends T> mapper, BiCollector<K, T, R> downstream) {

mug-guava/src/test/java/com/google/mu/util/stream/GuavaCollectorsTest.java

@@ -15,10 +15,12 @@
 package com.google.mu.util.stream;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.mu.util.Substring.first;
 import static com.google.mu.util.stream.BiCollectors.groupingBy;
 import static com.google.mu.util.stream.GuavaCollectors.flatteningToImmutableListMultimap;
 import static com.google.mu.util.stream.GuavaCollectors.flatteningToImmutableSetMultimap;
 import static com.google.mu.util.stream.GuavaCollectors.indexingBy;
+import static com.google.mu.util.stream.GuavaCollectors.toImmutableBiMap;
 import static com.google.mu.util.stream.GuavaCollectors.toImmutableListMultimap;
 import static com.google.mu.util.stream.GuavaCollectors.toImmutableMap;
 import static com.google.mu.util.stream.GuavaCollectors.toImmutableMultiset;
@@ -38,6 +40,7 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
+import com.google.common.collect.ImmutableBiMap;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMap;
@@ -191,6 +194,40 @@ public class GuavaCollectorsTest {
     assertThat(table.rowMap()).containsExactly("r1", ImmutableMap.of("c1", 11, "c2", 12)).inOrder();
   }
 
+  @Test public void testToImmutableMap_fromPairs() {
+    String input = "k1=v1,k2=v2";
+    ImmutableMap<String, String> kvs =
+        first(',').delimit(input).collect(toImmutableMap(s -> first('=').split(s).orElseThrow()));
+    assertThat(kvs).containsExactly("k1", "v1", "k2", "v2").inOrder();
+  }
+
+  @Test public void testToImmutableListMultimap_fromPairs() {
+    String input = "k1=v1,k2=v2,k2=v2";
+    ImmutableListMultimap<String, String> kvs =
+        first(',')
+            .delimit(input)
+            .collect(toImmutableListMultimap(s -> first('=').split(s).orElseThrow()));
+    assertThat(kvs).containsExactly("k1", "v1", "k2", "v2", "k2", "v2").inOrder();
+  }
+
+  @Test public void testToImmutableSetMultimap_fromPairs() {
+    String input = "k1=v1,k2=v2,k2=v3";
+    ImmutableSetMultimap<String, String> kvs =
+        first(',')
+            .delimit(input)
+            .collect(toImmutableSetMultimap(s -> first('=').split(s).orElseThrow()));
+    assertThat(kvs).containsExactly("k1", "v1", "k2", "v2", "k2", "v3").inOrder();
+  }
+
+  @Test public void testToImmutableBiMap_fromPairs() {
+    String input = "k1=v1,k2=v2";
+    ImmutableBiMap<String, String> kvs =
+        first(',')
+            .delimit(input)
+            .collect(toImmutableBiMap(s -> first('=').split(s).orElseThrow()));
+    assertThat(kvs).containsExactly("k1", "v1", "k2", "v2").inOrder();
+  }
+
   @Test public void testIndexingBy() {
     assertThat(Stream.of(1, 2).collect(indexingBy(Object::toString)))
         .containsExactly("1", 1, "2", 2)