runnable interface in thread

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in detail and simplest manner

!!!

We're much better at answering specific questions rather than trying to recreate tutorials and FAQs that already exist in internet-land. Google found me this which looks like a good place to start: Code Style: Java threads frequently asked questions (FAQ)
Why don't you have a look at this and other tutorials on-line, and then if you still have any specific points of misunderstanding, come on back and ask your specific questions. Much luck!