Working with the AtoMiC Toolkit

The java.util.concurrent.atomic package is a collection of 12 sub-classes that support operations on single variables that are thread-safe and lock-free. In this context, thread-safe refers to code that accesses or mutates a shared single variable without impeding on other threads executing on the variable at the same time. This superclass was introduced in Java 7.

Here is a list of the 12 sub-classes in the AtoMiC Toolkit. The class names, as you would expect, are self-descriptive:

Volatile variables, fields, and array elements can be asynchronously modified by concurrent threads.

Here is a code snippet that demonstrates the use of the volatile keyword for an instance variable:

    public class Sample 
    {
      private static volatile Sample myVolatileVariable; // a
       volatile instance variable

      public static Sample getVariable() // getter method
      {
        if (myVolatileVariable != null) 
        {
          return myVolatileVariable;
        }
        // this section executes if myVolatileVariable == null
        synchronized(Sample.class)
        {
          if (myVolatileVariable == null)
          {
            myVolatileVariable =  new Sample();
          }
        }
    }