Equals method must be symmetric and transitive.

briar-api/src/net/sf/briar/api/ContactId.java

@@ -16,14 +16,14 @@ public class ContactId {
 		return id;
 	}
 
+	@Override
+	public int hashCode() {
+		return id;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if(o instanceof ContactId) return id == ((ContactId) o).id;
 		return false;
 	}
-
-	@Override
-	public int hashCode() {
-		return id;
-	}
 }

briar-api/src/net/sf/briar/api/protocol/Transport.java

@@ -3,37 +3,40 @@ package net.sf.briar.api.protocol;
 import java.util.Map;
 import java.util.TreeMap;
 
-public class Transport extends TreeMap<String, String> {
-
-	private static final long serialVersionUID = 4900420175715429560L;
+public class Transport {
 
 	private final TransportId id;
+	private final TreeMap<String, String> properties;
 
 	public Transport(TransportId id, Map<String, String> p) {
-		super(p);
 		this.id = id;
+		properties = new TreeMap<String, String>(p);
 	}
 
 	public Transport(TransportId id) {
-		super();
 		this.id = id;
+		properties = new TreeMap<String, String>();
 	}
 
 	public TransportId getId() {
 		return id;
 	}
 
-	@Override
-	public int hashCode() {
-		return id.hashCode();
+	public Map<String, String> getProperties() {
+		return properties;
 	}
 
 	@Override
 	public boolean equals(Object o) {
 		if(o instanceof Transport) {
 			Transport t = (Transport) o;
-			return id.equals(t.id) && super.equals(o);
+			return id.equals(t.id) && properties.equals(t.properties);
 		}
 		return false;
 	}
+
+	@Override
+	public int hashCode() {
+		return id.hashCode();
+	}
 }