As discussed in Java multi-threading article we can define a thread in the following two ways:
- By extending Thread class
- By implementing Runnable interface
In the first approach, Our class always extends Thread class. There is no chance of extending any other class. Hence we are missing Inheritance benefits. In the second approach, while implementing Runnable interface we can extends any other class. Hence we are able to use the benefits of Inheritance.
Because of the above reasons, implementing Runnable interface approach is recommended than extending Thread class.
The significant differences between extending Thread class and implementing Runnable interface:
- When we extend Thread class, we can’t extend any other class even we require and When we implement Runnable, we can save a space for our class to extend any other class in future or now.
- When we extend Thread class, each of our thread creates unique object and associate with it. When we implements Runnable, it shares the same object to multiple threads.
Lets have a look on the below programs for better understanding:
Main method executed by main thread Run method executed by child Thread
Hello Visitors Main method executed by main thread Run method executed by child Thread
NOTE : In the case of multithreading we cant predict the exact order of output because it will vary from system to system or JVM to JVM.
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