SDE - 1

The naïve approach for this question is to run a loop from the start to the end number. And for each number, check if it is prime or not. If the number is prime, we print it otherwise skip it.

One optimization to this approach would be to skip all even numbers (except 2 if present in interval) since even numbers are not prime.
Function to check if a number is prime or not :
isPrime(n):
if (n <= 1) return false
for (i=2; i if (n%i == 0)
return false
}
return true

The idea is to create a copy of num and recursively pass the copy by reference, and pass num by value. In the recursive calls, divide num by 10 while moving down the recursion tree. While moving up the recursion tree, divide the copy by 10. When they meet in a function for which all child calls are over, the last digit of num will be ith digit from the beginning and the last digit of copy will be ith digit from the end.

Instance method can access the instance methods and instance variables directly.
Instance method can access static variables and static methods directly.
Static methods can access the static variables and static methods directly.
Static methods can’t access instance methods and instance variables directly. They must use reference to object. And static method can’t use this keyword as there is no instance for ‘this’ to refer to.

1) Abstract class can have abstract and non-abstract methods. Interface can have only abstract methods. Since Java 8, it can have default and static methods also.
2) Abstract class doesn't support multiple inheritance. Interface supports multiple inheritance.
3) Abstract class can have final, non-final, static and non-static variables. Interface has only static and final variables.
4) Abstract class can provide the implementation of interface. Interface can't provide the implementation of abstract class.
5) The abstract keyword is used to declare abstract class. The interface keyword is used to declare interface.
6) An abstract class can extend another Java class and implement multiple Java interfaces. An interface can extend another Java interface only.
7) An abstract class can be extended using keyword "extends". An interface can be implemented using keyword "implements".

1. As the name suggests, ClassNotFoundException is an exception while NoClassDefFoundError is an error.
2. ClassNotFoundException occurs when classpath does not get updated with required JAR files while error occurs when the required class definition is not present at runtime.

1 Type : 
Error : Classified as an unchecked type 
Exception : Classified as checked and unchecked 
2 Package :
Error : It belongs to java.lang.error 
Exception : It belongs to java.lang.Exception 
3 Recoverable/ Irrecoverable : 
Error : It is irrecoverable
Exception : It is recoverable
4 Error : It can't be occur at compile time 
Exception : It can occur at run time compile time both 
5 Example
Error : OutOfMemoryError ,IOError 
Exception : NullPointerException , SqlException

The serialization at runtime associates with each serializable class a version number called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization.

Following are the requirements: 

The class must be declared as final so that child classes can’t be created.
Data members in the class must be declared private so that direct access is not allowed.
Data members in the class must be declared as final so that we can’t change the value of it after object creation.
A parameterized constructor should initialize all the fields performing a deep copy so that data members can’t be modified with an object reference.
Deep Copy of objects should be performed in the getter methods to return a copy rather than returning the actual object reference)