What do you understand by Callable and Future in Java?

Answer

Java Callable interface: In Java5 callable interface was provided by the package java.util.concurrent. It is similar to the Runnable interface but it can return a result, and it can throw an Exception. It also provides a run() method for execution of a thread. Java Callable can return any object as it uses Generic.

Syntax:

public interface Callable<V>

Java Future interface: Java Future interface gives the result of a concurrent process. The Callable interface returns the object of java.util.concurrent.Future.

Java Future provides following methods for implementation.

• cancel(boolean mayInterruptIfRunning): It is used to cancel the execution of the assigned task.
• get(): It waits for the time if execution not completed and then retrieved the result.
• isCancelled(): It returns the Boolean value as it returns true if the task was canceled before the completion.
• isDone(): It returns true if the job is completed successfully else returns false.