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diff --git a/java/core/src/main/java/com/google/protobuf/MapEntryLite.java b/java/core/src/main/java/com/google/protobuf/MapEntryLite.java
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+++ b/java/core/src/main/java/com/google/protobuf/MapEntryLite.java
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+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+import java.util.AbstractMap;
+import java.util.Map;
+
+/**
+ * Implements the lite version of map entry messages.
+ *
+ * This class serves as an utility class to help do serialization/parsing of
+ * map entries. It's used in generated code and also in the full version
+ * MapEntry message.
+ *
+ * Protobuf internal. Users shouldn't use.
+ */
+public class MapEntryLite<K, V> {
+
+  static class Metadata<K, V> {
+    public final WireFormat.FieldType keyType;
+    public final K defaultKey;
+    public final WireFormat.FieldType valueType;
+    public final V defaultValue;
+
+    public Metadata(
+        WireFormat.FieldType keyType, K defaultKey,
+        WireFormat.FieldType valueType, V defaultValue) {
+      this.keyType = keyType;
+      this.defaultKey = defaultKey;
+      this.valueType = valueType;
+      this.defaultValue = defaultValue;
+    }
+  }
+
+  private static final int KEY_FIELD_NUMBER = 1;
+  private static final int VALUE_FIELD_NUMBER = 2;
+
+  private final Metadata<K, V> metadata;
+  private final K key;
+  private final V value;
+
+  /** Creates a default MapEntryLite message instance. */
+  private MapEntryLite(
+      WireFormat.FieldType keyType, K defaultKey,
+      WireFormat.FieldType valueType, V defaultValue) {
+    this.metadata = new Metadata<K, V>(keyType, defaultKey, valueType, defaultValue);
+    this.key = defaultKey;
+    this.value = defaultValue;
+  }
+
+  /** Creates a new MapEntryLite message. */
+  private MapEntryLite(Metadata<K, V> metadata, K key, V value) {
+    this.metadata = metadata;
+    this.key = key;
+    this.value = value;
+  }
+
+  public K getKey() {
+    return key;
+  }
+
+  public V getValue() {
+    return value;
+  }
+
+  /**
+   * Creates a default MapEntryLite message instance.
+   *
+   * This method is used by generated code to create the default instance for
+   * a map entry message. The created default instance should be used to create
+   * new map entry messages of the same type. For each map entry message, only
+   * one default instance should be created.
+   */
+  public static <K, V> MapEntryLite<K, V> newDefaultInstance(
+      WireFormat.FieldType keyType, K defaultKey,
+      WireFormat.FieldType valueType, V defaultValue) {
+    return new MapEntryLite<K, V>(
+        keyType, defaultKey, valueType, defaultValue);
+  }
+
+  static <K, V> void writeTo(CodedOutputStream output, Metadata<K, V> metadata, K key, V value)
+      throws IOException {
+    FieldSet.writeElement(output, metadata.keyType, KEY_FIELD_NUMBER, key);
+    FieldSet.writeElement(output, metadata.valueType, VALUE_FIELD_NUMBER, value);
+  }
+
+  static <K, V> int computeSerializedSize(Metadata<K, V> metadata, K key, V value) {
+    return FieldSet.computeElementSize(metadata.keyType, KEY_FIELD_NUMBER, key)
+        + FieldSet.computeElementSize(metadata.valueType, VALUE_FIELD_NUMBER, value);
+  }
+
+  @SuppressWarnings("unchecked")
+  static <T> T parseField(
+      CodedInputStream input, ExtensionRegistryLite extensionRegistry,
+      WireFormat.FieldType type, T value) throws IOException {
+    switch (type) {
+      case MESSAGE:
+        MessageLite.Builder subBuilder = ((MessageLite) value).toBuilder();
+        input.readMessage(subBuilder, extensionRegistry);
+        return (T) subBuilder.buildPartial();
+      case ENUM:
+        return (T) (java.lang.Integer) input.readEnum();
+      case GROUP:
+        throw new RuntimeException("Groups are not allowed in maps.");
+      default:
+        return (T) FieldSet.readPrimitiveField(input, type, true);
+    }
+  }
+
+  /**
+   * Serializes the provided key and value as though they were wrapped by a {@link MapEntryLite}
+   * to the output stream. This helper method avoids allocation of a {@link MapEntryLite}
+   * built with a key and value and is called from generated code directly.
+   */
+  public void serializeTo(CodedOutputStream output, int fieldNumber, K key, V value)
+      throws IOException {
+    output.writeTag(fieldNumber, WireFormat.WIRETYPE_LENGTH_DELIMITED);
+    output.writeUInt32NoTag(computeSerializedSize(metadata, key, value));
+    writeTo(output, metadata, key, value);
+  }
+
+  /**
+   * Computes the message size for the provided key and value as though they were wrapped
+   * by a {@link MapEntryLite}. This helper method avoids allocation of a {@link MapEntryLite}
+   * built with a key and value and is called from generated code directly.
+   */
+  public int computeMessageSize(int fieldNumber, K key, V value) {
+    return CodedOutputStream.computeTagSize(fieldNumber)
+        + CodedOutputStream.computeLengthDelimitedFieldSize(
+            computeSerializedSize(metadata, key, value));
+  }
+
+  /**
+   * Parses an entry off of the input as a {@link Map.Entry}. This helper requires an allocation
+   * so using {@link #parseInto} is preferred if possible.
+   */
+  public Map.Entry<K, V> parseEntry(ByteString bytes, ExtensionRegistryLite extensionRegistry)
+      throws IOException {
+    return parseEntry(bytes.newCodedInput(), metadata, extensionRegistry);
+  }
+
+  static <K, V> Map.Entry<K, V> parseEntry(
+      CodedInputStream input, Metadata<K, V> metadata, ExtensionRegistryLite extensionRegistry)
+          throws IOException{
+    K key = metadata.defaultKey;
+    V value = metadata.defaultValue;
+    while (true) {
+      int tag = input.readTag();
+      if (tag == 0) {
+        break;
+      }
+      if (tag == WireFormat.makeTag(KEY_FIELD_NUMBER, metadata.keyType.getWireType())) {
+        key = parseField(input, extensionRegistry, metadata.keyType, key);
+      } else if (tag == WireFormat.makeTag(VALUE_FIELD_NUMBER, metadata.valueType.getWireType())) {
+        value = parseField(input, extensionRegistry, metadata.valueType, value);
+      } else {
+        if (!input.skipField(tag)) {
+          break;
+        }
+      }
+    }
+    return new AbstractMap.SimpleImmutableEntry<K, V>(key, value);
+  }
+
+  /**
+   * Parses an entry off of the input into the map. This helper avoids allocaton of a
+   * {@link MapEntryLite} by parsing directly into the provided {@link MapFieldLite}.
+   */
+  public void parseInto(
+      MapFieldLite<K, V> map, CodedInputStream input, ExtensionRegistryLite extensionRegistry)
+          throws IOException {
+    int length = input.readRawVarint32();
+    final int oldLimit = input.pushLimit(length);
+    K key = metadata.defaultKey;
+    V value = metadata.defaultValue;
+
+    while (true) {
+      int tag = input.readTag();
+      if (tag == 0) {
+        break;
+      }
+      if (tag == WireFormat.makeTag(KEY_FIELD_NUMBER, metadata.keyType.getWireType())) {
+        key = parseField(input, extensionRegistry, metadata.keyType, key);
+      } else if (tag == WireFormat.makeTag(VALUE_FIELD_NUMBER, metadata.valueType.getWireType())) {
+        value = parseField(input, extensionRegistry, metadata.valueType, value);
+      } else {
+        if (!input.skipField(tag)) {
+          break;
+        }
+      }
+    }
+
+    input.checkLastTagWas(0);
+    input.popLimit(oldLimit);
+    map.put(key, value);
+  }
+}