Add #stream to sets:

exonum-java-binding/CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
   `ProofMapIndexProxy#getIndexHash` accordingly.
 
 ### Added
+- `stream` for sets: `KeySetIndex` and `ValueSetIndex`. (#1088)
 - Proofs of absence of an element with the specified index for `ProofListIndexProxy`. (#1081)
 
 ## [0.7.0] - 2019-07-17

exonum-java-binding/core/src/main/java/com/exonum/binding/core/storage/indices/KeySetIndexProxy.java

@@ -28,7 +28,11 @@
 import com.exonum.binding.core.util.LibraryLoader;
 import com.google.protobuf.MessageLite;
 import java.util.Iterator;
+import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.function.LongSupplier;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 /**
  * A key set is an index that contains no duplicate elements (keys).
@@ -61,6 +65,11 @@ public final class KeySetIndexProxy<E> extends AbstractIndexProxy implements Ite
     LibraryLoader.load();
   }
 
+  // Note that we do *not* specify Spliterator.DISTINCT because it is documented in terms
+  // of Object#equals which this set does not use.
+  private static final int BASE_SPLITERATOR_CHARACTERISTICS =
+      Spliterator.NONNULL | Spliterator.ORDERED;
+
   private final CheckingSerializerDecorator<E> serializer;
 
   /**
@@ -220,6 +229,25 @@ public Iterator<E> iterator() {
         serializer::fromBytes);
   }
 
+  /**
+   * Returns a stream of the set elements. The elements are ordered lexicographically.
+   *
+   * @throws IllegalStateException if this set is not valid
+   */
+  public Stream<E> stream() {
+    return StreamSupport.stream(
+        Spliterators.spliteratorUnknownSize(iterator(), streamCharacteristics()),
+        false);
+  }
+
+  private int streamCharacteristics() {
+    if (dbView.canModify()) {
+      return BASE_SPLITERATOR_CHARACTERISTICS;
+    } else {
+      return BASE_SPLITERATOR_CHARACTERISTICS | Spliterator.IMMUTABLE;
+    }
+  }
+
   /**
    * Removes the element from this set. If it's not in the set, does nothing.
    * 

exonum-java-binding/core/src/main/java/com/exonum/binding/core/storage/indices/ValueSetIndexProxy.java

@@ -33,7 +33,11 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.protobuf.MessageLite;
 import java.util.Iterator;
+import java.util.Spliterator;
+import java.util.Spliterators;
 import java.util.function.LongSupplier;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 import javax.annotation.Nullable;
 
 /**
@@ -68,6 +72,11 @@ public final class ValueSetIndexProxy<E> extends AbstractIndexProxy
     LibraryLoader.load();
   }
 
+  // Note that we do *not* specify Spliterator.DISTINCT because it is documented in terms
+  // of Object#equals which this set does not use.
+  private static final int BASE_SPLITERATOR_CHARACTERISTICS =
+      Spliterator.NONNULL | Spliterator.ORDERED;
+
   private final CheckingSerializerDecorator<E> serializer;
 
   /**
@@ -241,7 +250,7 @@ public Iterator<HashCode> hashes() {
 
   /**
    * Returns an iterator over the entries of this set. An entry is a hash-value pair.
-   * The entries are ordered by keys lexicographically.
+   * The entries are ordered by hashes lexicographically.
    *
    * @return an iterator over the entries of this set
    * @throws IllegalStateException if this set is not valid
@@ -263,6 +272,27 @@ public Iterator<Entry<E>> iterator() {
 
   private native void nativeIteratorFree(long iterNativeHandle);
 
+  /**
+   * Returns a stream of the entries in this set. An entry is a hash-value pair.
+   * The entries are ordered by hashes lexicographically.
+   *
+   * @throws IllegalStateException if this set is not valid
+   */
+  public Stream<Entry<E>> stream() {
+    return StreamSupport.stream(
+        Spliterators.spliteratorUnknownSize(iterator(), streamCharacteristics()),
+        false
+    );
+  }
+
+  private int streamCharacteristics() {
+    if (dbView.canModify()) {
+      return BASE_SPLITERATOR_CHARACTERISTICS;
+    } else {
+      return BASE_SPLITERATOR_CHARACTERISTICS | Spliterator.IMMUTABLE;
+    }
+  }
+
   /**
    * An entry of a value set index: a hash-value pair.
    *

exonum-java-binding/core/src/test/java/com/exonum/binding/core/storage/indices/KeySetIndexProxyIntegrationTest.java

@@ -19,6 +19,7 @@
 import static com.exonum.binding.core.storage.indices.TestStorageItems.K1;
 import static com.exonum.binding.core.storage.indices.TestStorageItems.K9;
 import static com.exonum.binding.core.storage.indices.TestStorageItems.V1;
+import static java.util.stream.Collectors.toList;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -112,6 +113,22 @@ void testIterator() {
     });
   }
 
+  @Test
+  void testStream() {
+    runTestWithView(database::createFork, (set) -> {
+      List<String> elements = TestStorageItems.keys;
+
+      elements.forEach(set::add);
+
+      List<String> streamElements = set.stream()
+          .collect(toList());
+
+      // Check that the stream includes all the elements added
+      // and that they appear in lexicographical order (the order of TestStorageItems.keys).
+      assertThat(streamElements, equalTo(elements));
+    });
+  }
+
   @Test
   void removesAddedElement() {
     runTestWithView(database::createFork, (set) -> {

exonum-java-binding/core/src/test/java/com/exonum/binding/core/storage/indices/ValueSetIndexProxyIntegrationTest.java

@@ -19,6 +19,7 @@
 import static com.exonum.binding.core.storage.indices.TestStorageItems.V1;
 import static com.exonum.binding.core.storage.indices.TestStorageItems.V2;
 import static com.exonum.binding.core.storage.indices.TestStorageItems.V9;
+import static java.util.stream.Collectors.toList;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -37,7 +38,6 @@
 import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.Function;
-import java.util.stream.Collectors;
 import org.junit.jupiter.api.Test;
 
 class ValueSetIndexProxyIntegrationTest
@@ -159,18 +159,33 @@ void testIterator() {
     });
   }
 
+  @Test
+  void testStream() {
+    runTestWithView(database::createFork, (set) -> {
+      List<String> elements = TestStorageItems.values;
+
+      elements.forEach(set::add);
+
+      List<ValueSetIndexProxy.Entry<String>> entriesFromStream = set.stream()
+          .collect(toList());
+      List<ValueSetIndexProxy.Entry<String>> entriesExpected = getOrderedEntries(elements);
+
+      assertThat(entriesFromStream, equalTo(entriesExpected));
+    });
+  }
+
   private static List<HashCode> getOrderedHashes(List<String> elements) {
     return getOrderedEntries(elements).stream()
         .map(ValueSetIndexProxy.Entry::getHash)
-        .collect(Collectors.toList());
+        .collect(toList());
   }
 
   private static List<ValueSetIndexProxy.Entry<String>> getOrderedEntries(List<String> elements) {
     return elements.stream()
         .map(value -> ValueSetIndexProxy.Entry.from(getHashOf(value), value))
         .sorted((e1, e2) -> UnsignedBytes.lexicographicalComparator()
             .compare(e1.getHash().asBytes(), e2.getHash().asBytes()))
-        .collect(Collectors.toList());
+        .collect(toList());
   }
 
   @Test