Return types should be co-varient.

The access specifier of the child class method should be either same or broader than parent class method.

If the parent class method throws any checked exception then child class method should throw the same checked exception or its child.

Inside Test class, we override interface default method. In overriding method resolution is always based on runtime object, but not based on the reference. Hence Test class method will be executed.

Variable resoution is always based on reference type but not based on runtime object. We used Parent reference and hence we will get 10.

char can be promoted to either int or double, but nearest promotion is int. Hence int argument method will be executed.

Interface static method by default not available to the implementation class. We should call by using interface name only.

When ever we are importing a package, all classes and interfaces present in that package are available to our program but not subpackage classes. Hence if we want to use sub package class, compulsory we have to write import statement until sub package level.

Every variable present in the interface is always final by default.

Hence in the implementation class we cannot modify value. Otherwise, we will get compile time error.

error: cannot assign a value to final variable x

x = 100;

If we declare return type for the constructor then it will be treated as a method and we won't get any compile time error. Hence public void Test()===> is a normal method but not constructor.

Overriding concept is not applicable for private methods. But based on our requirement, we can define same private method in the child class and it is its specific method.

java.lang package is by default available for every java source file and we are not required to import explicitly.