Thread-private lists in Java

I have a Thread sub-class called XmlProcessor that needs to accept some list or array of Strings to process. I need this list to be completely private to each thread, so that it isn't modified in any way by other threads. What is my best option?

Thanks, Ja开发者_JAVA技巧red

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Use the ThreadLocal class. It allows you to create references visible only by the current thread.

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If there is an instance of XmlProcessor per thread and the list is held as a private, it should be accessible from other threads so long as you: 1. don't provider a getter or setter method 2. ensure that the reference held by the instance is a copy of whatever was passed rather than just a pointer to the list that might be held by other objects.

You might consider using Guava's ImmutableList class to enforce this if the list cannot be changed.

http://docs.guava-libraries.googlecode.com/git-history/release09/javadoc/index.html

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Based on Jareds comment it seems you have something that looks like this.

public class MyClass extends Runnable{
   static ThreadLocal<List<String>> listBonds = new ThreadLocal<List<String>>();

   public MyClass (List<String> list){
        listBonds.set(list);
   }
   public void run(){
      listBonds.get(); // it returns null here?
   }

}

If my assumption is true then the reason listBonds.get() is null is because a different thread is accessing listBonds when you invoke set to when you invoke get

Image this

Thread 1:
  Thread myClass = new Thread(new MyClass(someList));
    listBonds.set(someList);
  myClass.start(); 
Thread 2: (MyClass)
  listBonds.get() --- A new thread is requesting the threadlocal variable and hence its null

If this is the case then the Runnable instance will be inherently thread-local/thread-safe and then you can have the List be an instance variable of the Runnable