From c5caeaea740e9b1a7a5da35e856bebbd947449c6 Mon Sep 17 00:00:00 2001
From: Mike Hearn <hearn@google.com>
Date: Sat, 21 Jul 2012 23:02:07 +0200
Subject: [PATCH] Duplicate channel futures list before closing channels.

Resolves issue 221
---
 .../src/main/java/com/google/bitcoin/core/PeerGroup.java | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
index a02d62671..8bf38b5a5 100644
--- a/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
+++ b/core/src/main/java/com/google/bitcoin/core/PeerGroup.java
@@ -501,10 +501,13 @@ public class PeerGroup {
             synchronized (PeerGroup.this) {
                 running = false;
                 shutdownPeerDiscovery();
+                LinkedList<ChannelFuture> futures;
                 synchronized (channelFutures) {
-                    for (ChannelFuture future : channelFutures.values()) {
-                        future.getChannel().close();
-                    }
+                    // Copy the list here because the act of closing the channel modifies the channelFutures map.
+                    futures = new LinkedList<ChannelFuture>(channelFutures.values());
+                }
+                for (ChannelFuture future : futures) {
+                    future.getChannel().close();
                 }
                 bootstrap.releaseExternalResources();
             }