There are two ways of creating a thread; extend (sub-class) the Thread class and implement the Runnable interface. For both of these ways you must implement (override and not overload) the public void run() method. (1) is correct - Extending the Thread class and overriding its run method is a valid procedure. (4) is correct - You must implement interfaces, and runnable is an interface and you must also include the run method. (2) is wrong - Runnable is an interface which implements not Extends. Gives the error: (No interface expected here) (3) is wrong - You cannot implement java.lang.Thread (This is a Class). (Implements Thread, gives the error: Interface expected). Implements expects an interface. (5) is wrong - You cannot implement java.lang.Thread (This is a class). You Extend classes, and Implement interfaces. (Implements Thread, gives the error: Interface expected)