Java: why Thread.sleep() and yield() are static?

Question

Why sleep() and yield() methods are defined as static methods in java.lang.Thread class?

Answer 1

They are static so that overriding concept can be avoided i.e.

When they are called with parent class reference to hold child class object like situation it implements Method Hiding concept and not overriding due to Static method nature, i.e parent class(here thread class) method will run which have the complete functionality of sleep and yield.

http://i.stack.imgur.com/goygW.jpg