I want to know what are the differences between runnable and thread class implementation except they are class and interface and how to decide which is better at what time ...

Thread vs. Runnable in Java 1) Java doesn't support multiple inheritance, which means you can only extend one class in Java so once you extended Thread class you lost your chance and can not extend or inherit another class in Java. 2) In Object oriented programming extending a class generally means adding new functionality, modifying or improving behaviors. If we are not making any modification on Thread than use Runnable interface instead. 3) Runnable interface represent a Task which can be executed by either plain Thread or Executors or any other means. So logical separation of Task as Runnable than Thread is good design decision. 4) Separating task as Runnable means we can reuse the task and also has liberty to execute it from different means. Since you cannot restart a Thread once it completes. Again Runnable vs Thread for task, Runnable are winner. 5) Java designer recognizes this and that's why Executors accept Runnable as Task and they have worker thread which executes those task. read less

Here are some of my thoughts on whether I should use Thread or Runnable for implementing task in Java, though you have another choice as "Callable" for implementing thread which we will discuss later. 1) Java doesn't support multiple inheritance, which means you can only extend one class in Java so once you extended Thread class you lost your chance and can not extend or inherit another class in Java. 2) In Object oriented programming extending a class generally means adding new functionality, modifying or improving behaviors. If we are not making any modification on Thread than use Runnable interface instead. 3) Runnable interface represent a Task which can be executed by either plain Thread or Executors or any other means. so logical separation of Task as Runnable than Thread is good design decision. 4) Separating task as Runnable means we can reuse the task and also has liberty to execute it from different means. since you can not restart a Thread once it completes. again Runnable vs Thread for task, Runnable is winner. 5) Java designer recognizes this and that's why Executors accept Runnable as Task and they have worker thread which executes those task. 6) Inheriting all Thread methods are additional overhead just for representing a Task which can can be done easily with Runnable. These were some of notable difference between Thread and Runnable in Java, if you know any other differences on Thread vs Runnable than please share it via comments. I personally use Runnable over Thread for this scenario and recommends to use Runnable or Callable interface based on your requirement. read less

Java doesn't support multiple inheritance, which means you can only extend one class in Java so once you extended Thread class you lost your chance andcan not extend or inherit another class in Java. But by implementing Runnable Interface we can get a chance to extends one more class. By extending Thread, each of your threads has a unique object associated with it, whereas implementing Runnable, many threads can share the same runnable instance. read less

Thread vs Runnable in Java is always been a confusing decision for beginners in java. Thread in Java seems easy in comparison of Runnable because you just deal with one class java.lang. Thread while in case of using Runnable to implement Thread you need to deal with both Thread and Runnable two classes. Though decision of using Runnable or Thread should be taken considering differences between Runnable and Thread and pros and cons of both approaches. This is also a very popular thread interview questions and most of interviewer are really interested to know what is your point of view while choosing Thread vs Runnable or opposite. In this java article we will try to point out some differences between Thread and Runnable in Java which will help you to take an informed decision. read less