Add JsonArray#collector for Stream<@nullable JsonElement>

Author: MukjepScarlet

gson/src/main/java/com/google/gson/JsonArray.java

@@ -18,11 +18,14 @@
 
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.gson.internal.NonNullElementWrapperList;
+import org.jspecify.annotations.Nullable;
+
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.stream.Collector;
 
 /**
  * A class representing an array type in JSON. An array is a list of {@link JsonElement}s each of
@@ -40,6 +43,25 @@
  * @author Joel Leitch
  */
 public final class JsonArray extends JsonElement implements Iterable<JsonElement> {
+  private static final Collector<@Nullable JsonElement, JsonArray, JsonArray> COLLECTOR =
+      Collector.of(
+          JsonArray::new,
+          JsonArray::add,
+          (left, right) -> {
+            left.addAll(right);
+            return left;
+          });
+
+  /**
+   * Returns a collector that accumulates {@link JsonElement}s into a {@code JsonArray}.
+   *
+   * @return a collector that accumulates {@link JsonElement}s into a {@code JsonArray}
+   * @since $next-version$
+   */
+  public static Collector<@Nullable JsonElement, ?, JsonArray> collector() {
+    return COLLECTOR;
+  }
+
   private final ArrayList<JsonElement> elements;
 
   /** Creates an empty JsonArray. */

gson/src/test/java/com/google/gson/JsonArrayTest.java

@@ -22,6 +22,7 @@
 import com.google.common.testing.EqualsTester;
 import com.google.gson.common.MoreAsserts;
 import java.math.BigInteger;
+import java.util.stream.Stream;
 import org.junit.Test;
 
 /**
@@ -354,4 +355,29 @@ public void testToString() {
     array.add(nestedObject);
     assertThat(array.toString()).isEqualTo("[null,NaN,\"a\\u0000\",[\"\\\"\"],{\"n\\u0000\":1}]");
   }
+
+  @Test
+  public void testCollector() {
+    JsonArray array = Stream.of(new JsonPrimitive(1), new JsonArray(), null, new JsonObject())
+        .collect(JsonArray.collector());
+    assertThat(array).hasSize(4);
+    assertThat(array.get(0).getAsInt()).isEqualTo(1);
+    assertThat(array.get(1).isJsonArray()).isTrue();
+    assertThat(array.get(2).isJsonNull()).isTrue();
+    assertThat(array.get(3).isJsonObject()).isTrue();
+  }
+
+  @Test
+  public void testCollectorParallel() {
+    JsonArray array = Stream.iterate(0, i -> i + 1)
+        .limit(20)
+        .parallel()
+        .map(JsonPrimitive::new)
+        .collect(JsonArray.collector());
+
+    assertThat(array).hasSize(20);
+    for (int i = 0; i < 20; i++) {
+      assertThat(array.get(i).getAsInt()).isEqualTo(i);
+    }
+  }
 }

pom.xml

@@ -81,6 +81,13 @@
 
   <dependencyManagement>
     <dependencies>
+      <dependency>
+        <groupId>org.jspecify</groupId>
+        <artifactId>jspecify</artifactId>
+        <version>1.0.0</version>
+        <scope>provided</scope>
+      </dependency>
+
       <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>