Add thread safety warning to JavaDocs of entire Message class hierarchy.

core/src/main/java/org/bitcoinj/core/AddressMessage.java

@@ -24,9 +24,11 @@ import java.util.Collections;
 import java.util.List;
 
 /**
- * Represents an "addr" message on the P2P network, which contains broadcast IP addresses of other peers. This is
+ * <p>Represents an "addr" message on the P2P network, which contains broadcast IP addresses of other peers. This is
  * one of the ways peers can find each other without using the DNS or IRC discovery mechanisms. However storing and
- * using addr messages is not presently implemented.
+ * using addr messages is not presently implemented.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class AddressMessage extends Message {
 

core/src/main/java/org/bitcoinj/core/AlertMessage.java

@@ -33,7 +33,9 @@ import java.util.Set;
  * that software upgrades could be distributed independently of a hard-coded website, in order to allow everything to
  * be purely peer-to-peer. You don't have to use this of course, and indeed it often makes more sense not to.<p>
  *     
- * Before doing anything with an alert, you should check {@link AlertMessage#isSignatureValid()}.
+ * <p>Before doing anything with an alert, you should check {@link AlertMessage#isSignatureValid()}.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class AlertMessage extends Message {
     private byte[] content;

core/src/main/java/org/bitcoinj/core/Block.java

@@ -38,8 +38,10 @@ import static org.bitcoinj.core.Sha256Hash.*;
  * <a href="http://www.bitcoin.org/bitcoin.pdf">the Bitcoin technical paper</a> for
  * more detail on blocks. <p/>
  *
- * To get a block, you can either build one from the raw bytes you can get from another implementation, or request one
- * specifically using {@link Peer#getBlock(Sha256Hash)}, or grab one from a downloaded {@link BlockChain}.
+ * <p>To get a block, you can either build one from the raw bytes you can get from another implementation, or request one
+ * specifically using {@link Peer#getBlock(Sha256Hash)}, or grab one from a downloaded {@link BlockChain}.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class Block extends Message {
     /**

core/src/main/java/org/bitcoinj/core/BloomFilter.java

@@ -40,6 +40,8 @@ import static java.lang.Math.*;
  * match transactions that weren't inserted into it, but it will never fail to match transactions that were. This is
  * a useful privacy feature - if you have spare bandwidth the false positive rate can be increased so the remote peer
  * gets a noisy picture of what transactions are relevant to your wallet.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class BloomFilter extends Message {
     /** The BLOOM_UPDATE_* constants control when the bloom filter is auto-updated by the peer using

core/src/main/java/org/bitcoinj/core/ChildMessage.java

@@ -18,8 +18,10 @@ package org.bitcoinj.core;
 import javax.annotation.Nullable;
 
 /**
- * Represents a Message type that can be contained within another Message.  ChildMessages that have a cached
- * backing byte array need to invalidate their parent's caches as well as their own if they are modified.
+ * <p>Represents a Message type that can be contained within another Message.  ChildMessages that have a cached
+ * backing byte array need to invalidate their parent's caches as well as their own if they are modified.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public abstract class ChildMessage extends Message {
 

core/src/main/java/org/bitcoinj/core/EmptyMessage.java

@@ -21,8 +21,10 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 /**
- * Parent class for header only messages that don't have a payload.
- * Currently this includes getaddr, verack and special bitcoinj class UnknownMessage.
+ * <p>Parent class for header only messages that don't have a payload.
+ * Currently this includes getaddr, verack and special bitcoinj class UnknownMessage.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public abstract class EmptyMessage extends Message {
 

core/src/main/java/org/bitcoinj/core/FilteredBlock.java

@@ -25,6 +25,8 @@ import java.util.*;
 /**
  * <p>A FilteredBlock is used to relay a block with its transactions filtered using a {@link BloomFilter}. It consists
  * of the block header and a {@link PartialMerkleTree} which contains the transactions which matched the filter.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class FilteredBlock extends Message {
     private Block header;

core/src/main/java/org/bitcoinj/core/GetAddrMessage.java

@@ -17,8 +17,10 @@
 package org.bitcoinj.core;
 
 /**
- * Represents the "getaddr" P2P protocol message, which requests network {@link AddressMessage}s from a peer. Not to
- * be confused with {@link Address} which is sort of like an account number.
+ * <p>Represents the "getaddr" P2P protocol message, which requests network {@link AddressMessage}s from a peer. Not to
+ * be confused with {@link Address} which is sort of like an account number.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class GetAddrMessage extends EmptyMessage {
 

core/src/main/java/org/bitcoinj/core/GetBlocksMessage.java

@@ -23,8 +23,10 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
- * Represents the "getblocks" P2P network message, which requests the hashes of the parts of the block chain we're
- * missing. Those blocks can then be downloaded with a {@link GetDataMessage}.
+ * <p>Represents the "getblocks" P2P network message, which requests the hashes of the parts of the block chain we're
+ * missing. Those blocks can then be downloaded with a {@link GetDataMessage}.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class GetBlocksMessage extends Message {
 

core/src/main/java/org/bitcoinj/core/GetDataMessage.java

@@ -17,8 +17,10 @@
 package org.bitcoinj.core;
 
 /**
- * Represents the "getdata" P2P network message, which requests the contents of blocks or transactions given their
- * hashes.
+ * <p>Represents the "getdata" P2P network message, which requests the contents of blocks or transactions given their
+ * hashes.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class GetDataMessage extends ListMessage {
 

core/src/main/java/org/bitcoinj/core/GetHeadersMessage.java

@@ -19,10 +19,12 @@ package org.bitcoinj.core;
 import java.util.List;
 
 /**
- * The "getheaders" command is structurally identical to "getblocks", but has different meaning. On receiving this
+ * <p>The "getheaders" command is structurally identical to "getblocks", but has different meaning. On receiving this
  * message a Bitcoin node returns matching blocks up to the limit, but without the bodies. It is useful as an
  * optimization: when your wallet does not contain any keys created before a particular time, you don't have to download
- * the bodies for those blocks because you know there are no relevant transactions.
+ * the bodies for those blocks because you know there are no relevant transactions.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class GetHeadersMessage extends GetBlocksMessage {
     public GetHeadersMessage(NetworkParameters params, List<Sha256Hash> locator, Sha256Hash stopHash) {

core/src/main/java/org/bitcoinj/core/GetUTXOsMessage.java

@@ -37,6 +37,8 @@ import java.util.List;
  * space and time. If you want to look up unspent outputs by address, you can either query a block explorer site,
  * or you can use the {@link FullPrunedBlockChain} class to build the required indexes yourself. Bear in that it will
  * be quite slow and disk intensive to do that!</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class GetUTXOsMessage extends Message {
     public static final int MIN_PROTOCOL_VERSION = 70002;

core/src/main/java/org/bitcoinj/core/HeadersMessage.java

@@ -27,9 +27,11 @@ import java.util.Arrays;
 import java.util.List;
 
 /**
- * A protocol message that contains a repeated series of block headers, sent in response to the "getheaders" command.
+ * <p>A protocol message that contains a repeated series of block headers, sent in response to the "getheaders" command.
  * This is useful when you want to traverse the chain but know you don't care about the block contents, for example,
- * because you have a freshly created wallet with no keys.
+ * because you have a freshly created wallet with no keys.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class HeadersMessage extends Message {
     private static final Logger log = LoggerFactory.getLogger(HeadersMessage.class);

core/src/main/java/org/bitcoinj/core/InventoryMessage.java

@@ -23,6 +23,8 @@ import static com.google.common.base.Preconditions.checkArgument;
  * a bandwidth optimization - on receiving some data, a (fully validating) peer sends every connected peer an inv
  * containing the hash of what it saw. It'll only transmit the full thing if a peer asks for it with a
  * {@link GetDataMessage}.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class InventoryMessage extends ListMessage {
 

core/src/main/java/org/bitcoinj/core/ListMessage.java

@@ -24,7 +24,9 @@ import java.util.Collections;
 import java.util.List;
 
 /**
- * Abstract superclass of classes with list based payload, ie InventoryMessage and GetDataMessage.
+ * <p>Abstract superclass of classes with list based payload, ie InventoryMessage and GetDataMessage.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public abstract class ListMessage extends Message {
 

core/src/main/java/org/bitcoinj/core/MemoryPoolMessage.java

@@ -21,11 +21,13 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 /**
- * The "mempool" message asks a remote peer to announce all transactions in its memory pool, possibly restricted by
+ * <p>The "mempool" message asks a remote peer to announce all transactions in its memory pool, possibly restricted by
  * any Bloom filter set on the connection. The list of transaction hashes comes back in an inv message. Note that
  * this is different to the {@link TxConfidenceTable} object which doesn't try to keep track of all pending transactions,
  * it's just a holding area for transactions that a part of the app may find interesting. The mempool message has
- * no fields.
+ * no fields.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class MemoryPoolMessage extends Message {
     @Override

core/src/main/java/org/bitcoinj/core/Message.java

@@ -30,6 +30,8 @@ import static com.google.common.base.Preconditions.checkState;
  * <p>A Message is a data structure that can be serialized/deserialized using the Bitcoin serialization format.
  * Specific types of messages that are used both in the block chain, and on the wire, are derived from this
  * class.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public abstract class Message {
     private static final Logger log = LoggerFactory.getLogger(Message.class);

core/src/main/java/org/bitcoinj/core/NotFoundMessage.java

@@ -20,8 +20,10 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
- * Sent by a peer when a getdata request doesn't find the requested data in the mempool. It has the same format
- * as an inventory message and lists the hashes of the missing items.
+ * <p>Sent by a peer when a getdata request doesn't find the requested data in the mempool. It has the same format
+ * as an inventory message and lists the hashes of the missing items.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class NotFoundMessage extends InventoryMessage {
     public static int MIN_PROTOCOL_VERSION = 70001;

core/src/main/java/org/bitcoinj/core/PartialMerkleTree.java

@@ -52,6 +52,8 @@ import com.google.common.base.Objects;
  *  - varint     number of bytes of flag bits (1-3 bytes)
  *  - byte[]     flag bits, packed per 8 in a byte, least significant bit first (<= 2*N-1 bits)
  * The size constraints follow from this.</pre></p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class PartialMerkleTree extends Message {
     // the total number of transactions in the block

core/src/main/java/org/bitcoinj/core/PeerAddress.java

@@ -33,8 +33,10 @@ import static org.bitcoinj.core.Utils.uint64ToByteStreamLE;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
- * A PeerAddress holds an IP address and port number representing the network location of
- * a peer in the Bitcoin P2P network. It exists primarily for serialization purposes.
+ * <p>A PeerAddress holds an IP address and port number representing the network location of
+ * a peer in the Bitcoin P2P network. It exists primarily for serialization purposes.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class PeerAddress extends ChildMessage {
 

core/src/main/java/org/bitcoinj/core/Ping.java

@@ -20,6 +20,9 @@ package org.bitcoinj.core;
 import java.io.IOException;
 import java.io.OutputStream;
 
+/**
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
+ */
 public class Ping extends Message {
     private long nonce;
     private boolean hasNonce;

core/src/main/java/org/bitcoinj/core/Pong.java

@@ -20,6 +20,9 @@ package org.bitcoinj.core;
 import java.io.IOException;
 import java.io.OutputStream;
 
+/**
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
+ */
 public class Pong extends Message {
     private long nonce;
 

core/src/main/java/org/bitcoinj/core/RejectMessage.java

@@ -23,7 +23,9 @@ import java.io.OutputStream;
 import java.util.Locale;
 
 /**
- * A message sent by nodes when a message we sent was rejected (ie a transaction had too little fee/was invalid/etc)
+ * <p>A message sent by nodes when a message we sent was rejected (ie a transaction had too little fee/was invalid/etc).</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class RejectMessage extends Message {
 

core/src/main/java/org/bitcoinj/core/Transaction.java

@@ -54,6 +54,8 @@ import java.math.BigInteger;
  * Whether to trust a transaction is something that needs to be decided on a case by case basis - a rule that makes
  * sense for selling MP3s might not make sense for selling cars, or accepting payments from a family member. If you
  * are building a wallet, how to present confidence to your users is something to consider carefully.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class Transaction extends ChildMessage {
     /**

core/src/main/java/org/bitcoinj/core/TransactionInput.java

@@ -36,10 +36,12 @@ import static com.google.common.base.Preconditions.checkElementIndex;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
- * A transfer of coins from one address to another creates a transaction in which the outputs
+ * <p>A transfer of coins from one address to another creates a transaction in which the outputs
  * can be claimed by the recipient in the input of another transaction. You can imagine a
  * transaction as being a module which is wired up to others, the inputs of one have to be wired
- * to the outputs of another. The exceptions are coinbase transactions, which create new coins.
+ * to the outputs of another. The exceptions are coinbase transactions, which create new coins.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class TransactionInput extends ChildMessage {
     /** Magic sequence number that indicates there is no sequence number. */

core/src/main/java/org/bitcoinj/core/TransactionOutPoint.java

@@ -27,7 +27,9 @@ import java.io.*;
 import static com.google.common.base.Preconditions.*;
 
 /**
- * This message is a reference or pointer to an output of a different transaction.
+ * <p>This message is a reference or pointer to an output of a different transaction.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class TransactionOutPoint extends ChildMessage {
 

core/src/main/java/org/bitcoinj/core/TransactionOutput.java

@@ -28,8 +28,10 @@ import java.util.*;
 import static com.google.common.base.Preconditions.*;
 
 /**
- * A TransactionOutput message contains a scriptPubKey that controls who is able to spend its value. It is a sub-part
- * of the Transaction message.
+ * <p>A TransactionOutput message contains a scriptPubKey that controls who is able to spend its value. It is a sub-part
+ * of the Transaction message.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class TransactionOutput extends ChildMessage {
     private static final Logger log = LoggerFactory.getLogger(TransactionOutput.class);

core/src/main/java/org/bitcoinj/core/UTXOsMessage.java

@@ -38,6 +38,8 @@ import java.util.List;
  * if the data is occasionally wrong. Bear in mind that the answer can be wrong even in the absence of malicious intent
  * just through the nature of querying an ever changing data source: the UTXO set may be updated by a new transaction
  * immediately after this message is returned.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class UTXOsMessage extends Message {
     private long height;

core/src/main/java/org/bitcoinj/core/UnknownMessage.java

@@ -17,6 +17,9 @@
 
 package org.bitcoinj.core;
 
+/**
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
+ */
 public class UnknownMessage extends EmptyMessage {
 
     private String name;

core/src/main/java/org/bitcoinj/core/VersionAck.java

@@ -17,8 +17,10 @@
 package org.bitcoinj.core;
 
 /**
- * The verack message, sent by a client accepting the version message they
- * received from their peer.
+ * <p>The verack message, sent by a client accepting the version message they
+ * received from their peer.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class VersionAck extends EmptyMessage {
     public VersionAck() {

core/src/main/java/org/bitcoinj/core/VersionMessage.java

@@ -25,13 +25,15 @@ import java.net.UnknownHostException;
 import java.util.Locale;
 
 /**
- * A VersionMessage holds information exchanged during connection setup with another peer. Most of the fields are not
+ * <p>A VersionMessage holds information exchanged during connection setup with another peer. Most of the fields are not
  * particularly interesting. The subVer field, since BIP 14, acts as a User-Agent string would. You can and should 
  * append to or change the subVer for your own software so other implementations can identify it, and you can look at
- * the subVer field received from other nodes to see what they are running. <p>
+ * the subVer field received from other nodes to see what they are running.</p>
  *
- * After creating yourself a VersionMessage, you can pass it to {@link PeerGroup#setVersionMessage(VersionMessage)}
- * to ensure it will be used for each new connection.
+ * <p>After creating yourself a VersionMessage, you can pass it to {@link PeerGroup#setVersionMessage(VersionMessage)}
+ * to ensure it will be used for each new connection.</p>
+ * 
+ * <p>Instances of this class are not safe for use by multiple threads.</p>
  */
 public class VersionMessage extends Message {