Protocol Buffers are a way of encoding structured data in an efficient yet extensible format. Google uses Protocol Buffers for almost all of its internal RPC protocols and file formats.

JAR File Size and Download Location:

File name: protobuf-java.jar, protobuf-java-2.5.0.jar
File size: 533455 bytes
Date modified: 27-Feb-2013
Download: Protocol Buffers

Manifest of the JAR:

Bnd-LastModified: 1362700108682
Build-Jdk: 1.7.0-google-v5
Built-By: xiaofeng
Bundle-Description: Protocol Buffers are a way of encoding structured
 data in an efficient yet extensible format.
Bundle-DocURL: http://code.google.com/p/protobuf
Bundle-License: http://www.opensource.org/licenses/bsd-license.php
Bundle-ManifestVersion: 2
Bundle-Name: Protocol Buffer Java API
Bundle-SymbolicName: com.google.protobuf
Bundle-Vendor: Google
Bundle-Version: 2.5.0
Export-Package: com.google.protobuf;version="2.5.0"
Tool: Bnd-1.50.0

List of Classes in the JAR:

com/google/protobuf/AbstractMessage
com/google/protobuf/AbstractMessageLite
com/google/protobuf/AbstractParser
com/google/protobuf/BlockingRpcChannel
com/google/protobuf/BlockingService
com/google/protobuf/BoundedByteString
com/google/protobuf/ByteString
com/google/protobuf/CodedInputStream
com/google/protobuf/CodedOutputStream
com/google/protobuf/DescriptorProtos
com/google/protobuf/Descriptors
com/google/protobuf/DynamicMessage
com/google/protobuf/ExtensionRegistry
com/google/protobuf/ExtensionRegistryLite
com/google/protobuf/FieldSet
com/google/protobuf/GeneratedMessage
com/google/protobuf/GeneratedMessageLite
com/google/protobuf/Internal
com/google/protobuf/InvalidProtocolBufferException
com/google/protobuf/LazyField
com/google/protobuf/LazyStringArrayList
com/google/protobuf/LazyStringList
com/google/protobuf/LiteralByteString
com/google/protobuf/Message
com/google/protobuf/MessageLite
com/google/protobuf/MessageLiteOrBuilder
com/google/protobuf/MessageOrBuilder
com/google/protobuf/Parser
com/google/protobuf/ProtocolMessageEnum
com/google/protobuf/RepeatedFieldBuilder
com/google/protobuf/RopeByteString
com/google/protobuf/RpcCallback
com/google/protobuf/RpcChannel
com/google/protobuf/RpcController
com/google/protobuf/RpcUtil
com/google/protobuf/Service
com/google/protobuf/ServiceException
com/google/protobuf/SingleFieldBuilder
com/google/protobuf/SmallSortedMap
com/google/protobuf/TextFormat
com/google/protobuf/UninitializedMessageException
com/google/protobuf/UnknownFieldSet
com/google/protobuf/UnmodifiableLazyStringList
com/google/protobuf/Utf8
com/google/protobuf/WireFormat