Multiple threads from one host thread modify same object in host thread

Question

I am trying to start N threads from one 'host' thread, and as they execute they have to add elements to the same collection in the original 'host' thread. (Execute a compare method and if it returns true, they add the element they were comparing to the collection).

Now, if I have X 'host' threads, is there any way to differentiate between the X instances of the collection in the host thread, or is the only way to keep a map with X entries mapping the 'host' thread to its respective collection? This seems to be a very back door way.

Why are different instances associated with each host thread? What is each host thread associated with? (For example, if each host thread is associated with a particular database/connection/client/whatever, then the class for the database/connection/client/whatever should hold the collection.) — David Schwartz
– David Schwartz, Commented Jul 2, 2014 at 21:11
Can't the host thread tell the other threads it starts, "Here is the particular instance of this collection type that I'm using?" — David K
– David K, Commented Jul 2, 2014 at 21:21
I am trying to compare potentially massive binary trees created at initialization from a SQL query. Idea is create all trees once, so you never have to query the data base again during run time. I figured since each tree has a massive number of nodes, comparing them in parallel would make sense. Now, what if I want to perform multiple tree comparisons in parallel as well and pull all duplicate nodes in respective collections? Its part of my side/pet project. edit: I am basically trying to keep a separate collection associated with each comparison. — user3746152
– user3746152, Commented Jul 2, 2014 at 21:23
First of all, post some code to show us what you're talking about. Second of all, a collection can not be in a thread. A collection is in the heap. You may have one designated thread that is responsible for the collection in some way, but that is not a containment relationship. — Solomon Slow
– Solomon Slow, Commented Jul 2, 2014 at 22:03

Highland Mark · Accepted Answer · 2014-07-03 07:47:00Z

1

It is possible that ThreadLocal might be what you need to allow each of your host threads to have its own version of the collection.

answered Jul 3, 2014 at 7:47

Highland Mark

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Highland Mark · Accepted Answer · 2014-07-03 07:44:01Z

0

Have a look at Threads call. It is a way for each host thread to have a unique instance of an object - in this case your collection.

answered Jul 3, 2014 at 7:44

Highland Mark

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