We are invocing int-arg constructor which internally calls double-arg constructor. Hence the output is : 21

Reference to Date is ambiguous and hence we will get compile time error.

The first line inside every constructor should be either super() or this(). If we are not taking anything, then compiler will always place super().

If a class implements an interface, then compulsory we should provide implementation for every abstract method, otherwise we have to declare class as abstract. Every interface method is public and hence at the time of implementation we should declare as public only.

Overloaded methods must have same name but different argument types. Return types need not be same.

The correct order of statements in java source file is : package, import, class We cannot declared top level class as private and protected.

The main objective of introducing default methods in interfaces as the part of java 1.8 is, we can extend functionality of interface by adding new methods without effecting implementation classes.

Every interface method is by default public. Hence we cannot use private and protected modifiers.

char can be promoted to int type hence int-argument method will be executed for the first method call.

boolean will be converted to Object (boolean->Boolean->Object) and Object-argument method will be executed for the second method call.

double will be converted to Object (double->Double->Object) and Object-argument method will be executed for the third method call. Hence the output is: intObjectObject

We cannot declare abstract method with final, private, and static modifiers.