A callable interface was added in Java 5 to complement the existing Runnable interface, which is used to wrap a task and pass it to a Thread or thread pool for asynchronous execution. Callable actually represents an asynchronous computation, whose value is available via a Future object. All the code which needs to be executed asynchronously goes into the call() method. Callable is also a single abstract method type (SAM type), so it can be used along with lambda expression on Java 8. Both Callable and Future are parametric types and can be used to wrap classes like Integer, String, or anything else.
