Difference between Callable and Runnable interface in Java is one of the interesting questions from my list of Top 15 Java multi-threading questions, and it’s also very popular in various Java Interviews. The Callable interface is newer than Runnable interface and added on Java 5 release along with other major changes e.g. Generics, Enum, Static imports and variable argument method. Though both Callable and Runnable interface are designed to represent a task, which can be executed by any thread, there is some significant difference between them. In my opinion, the major difference between Callable and Runnable interface is that Callable can return the result of an operation performed inside call() method, which was one of the limitations with Runnable interface.
Another significant difference between Runnable and Callable interface is the ability to throw checked exception. The Callable interface can throw checked exception because it's call method throws Exception.
Commonly FutureTask is used along with Callable to get the result of an asynchronous computation task performed in call() method.
Callable vs Runnable interface in Java
As I explained major differences between a Callable and Runnable interface in the last section. Sometimes this question is also asked as the difference between call() and run() method in Java. All the points discussed here is equally related to that question as well. Let's see them in point format for better understanding :
1) The Runnable interface is older than Callable, there from JDK 1.0, while Callable is added on Java 5.0.
2) Runnable interface has run() method to define task while Callable interface uses call() method for task definition.
3) run() method does not return any value, it's return type is void while call method returns value. The Callable interface is a generic parameterized interface and Type of value is provided when an instance of Callable implementation is created.
4) Another difference on run and call method is that run method can not throw checked exception while call method can throw checked exception in Java.
Thats all the differences between Callable and Runnable in Java:
