change getChildren return type (#1674)

Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/BranchNode.java

@@ -76,8 +76,8 @@ class BranchNode<V> implements Node<V> {
   }
 
   @Override
-  public Optional<List<Node<V>>> getChildren() {
+  public List<Node<V>> getChildren() {
-    return Optional.of(Collections.unmodifiableList(children));
+    return Collections.unmodifiableList(children);
   }
 
   public Node<V> child(final byte index) {

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/ExtensionNode.java

@@ -64,8 +64,8 @@ class ExtensionNode<V> implements Node<V> {
   }
 
   @Override
-  public Optional<List<Node<V>>> getChildren() {
+  public List<Node<V>> getChildren() {
-    return Optional.of(Collections.singletonList(child));
+    return Collections.singletonList(child);
   }
 
   public Node<V> getChild() {

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/LeafNode.java

@@ -21,6 +21,7 @@ import tech.pegasys.pantheon.util.bytes.BytesValue;
 
 import java.lang.ref.SoftReference;
 import java.lang.ref.WeakReference;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
@@ -66,8 +67,8 @@ class LeafNode<V> implements Node<V> {
   }
 
   @Override
-  public Optional<List<Node<V>>> getChildren() {
+  public List<Node<V>> getChildren() {
-    return Optional.empty();
+    return Collections.emptyList();
   }
 
   @Override

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/Node.java

@@ -28,7 +28,7 @@ public interface Node<V> {
 
   Optional<V> getValue();
 
-  Optional<List<Node<V>>> getChildren();
+  List<Node<V>> getChildren();
 
   BytesValue getRlp();
 

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/NullNode.java

@@ -15,6 +15,7 @@ package tech.pegasys.pantheon.ethereum.trie;
 import tech.pegasys.pantheon.util.bytes.Bytes32;
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 
@@ -50,8 +51,8 @@ class NullNode<V> implements Node<V> {
   }
 
   @Override
-  public Optional<List<Node<V>>> getChildren() {
+  public List<Node<V>> getChildren() {
-    return Optional.empty();
+    return Collections.emptyList();
   }
 
   @Override

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/StoredNode.java

@@ -65,7 +65,7 @@ class StoredNode<V> implements Node<V> {
   }
 
   @Override
-  public Optional<List<Node<V>>> getChildren() {
+  public List<Node<V>> getChildren() {
     return load().getChildren();
   }
 

ethereum/trie/src/main/java/tech/pegasys/pantheon/ethereum/trie/TrieNodeDecoder.java

@@ -57,7 +57,7 @@ public class TrieNodeDecoder {
     nodes.add(node);
 
     final List<Node<BytesValue>> toProcess = new ArrayList<>();
-    node.getChildren().ifPresent(toProcess::addAll);
+    toProcess.addAll(node.getChildren());
     while (!toProcess.isEmpty()) {
       final Node<BytesValue> currentNode = toProcess.remove(0);
       if (Objects.equals(NullNode.instance(), currentNode)) {
@@ -68,7 +68,7 @@ public class TrieNodeDecoder {
 
       if (!currentNode.isReferencedByHash()) {
         // If current node is inlined, that means we can process its children
-        currentNode.getChildren().ifPresent(toProcess::addAll);
+        toProcess.addAll(currentNode.getChildren());
       }
     }
 
@@ -140,7 +140,7 @@ public class TrieNodeDecoder {
       final Node<BytesValue> nextNode = currentNodes.remove(0);
 
       final List<Node<BytesValue>> children = new ArrayList<>();
-      nextNode.getChildren().ifPresent(children::addAll);
+      children.addAll(nextNode.getChildren());
       while (!children.isEmpty()) {
         Node<BytesValue> child = children.remove(0);
         if (Objects.equals(child, NullNode.instance())) {

ethereum/trie/src/test/java/tech/pegasys/pantheon/ethereum/trie/TrieNodeDecoderTest.java

@@ -114,7 +114,7 @@ public class TrieNodeDecoderTest {
     assertThat(depth0And1Nodes.get(0).getHash()).isEqualTo(rootNode.getHash());
     // Subsequent nodes should be children of root node
     List<Bytes32> expectedNodesHashes =
-        rootNode.getChildren().get().stream()
+        rootNode.getChildren().stream()
             .filter(n -> !Objects.equals(n, NullNode.instance()))
             .map(Node::getHash)
             .collect(Collectors.toList());