Decipher Zone Technologies Interview Questions and Answers

The final keyword in Java is used to restrict the user from changing the value of a variable, making a method not overrideable, or preventing a class from being subclassed.

• Final variables cannot be reassigned once initialized

• Final methods cannot be overridden in subclasses

• Final classes cannot be subclassed

• Final parameters in a method cannot be modified within the method

In Java, == compares memory addresses while .equals() compares the actual values of objects.

• == compares memory addresses of objects

• .equals() compares the actual values of objects

• Use == for comparing primitive data types

• Use .equals() for comparing objects like Strings

The '==' operator compares memory addresses of objects, while the .equals() method compares the content or value of objects.

• Use '==' for comparing memory addresses of objects.

• Use .equals() for comparing the content or value of objects.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will return false, but str1.equals(str2) will return true.

Java program to check if a number is prime

• Create a function that takes an integer as input

• Check if the number is less than 2, return false

• Iterate from 2 to the square root of the number, check for divisibility

• If the number is divisible by any number, return false

• Otherwise, return true

A prime number is a number greater than 1 that can only be divided by 1 and itself.

• Prime numbers are integers greater than 1

• They have only two factors: 1 and the number itself

• Examples of prime numbers: 2, 3, 5, 7, 11, 13

HashMap is not thread-safe and allows null keys/values, while ConcurrentHashMap is thread-safe and does not allow null keys/values.

• HashMap is not thread-safe and can lead to ConcurrentModificationException if modified while iterating.

• ConcurrentHashMap uses internal locking mechanisms to provide thread-safety.

• ConcurrentHashMap does not allow null keys/values, while HashMap does.

• ConcurrentHashMap is more suitable for con

JVM optimizes method calls using various techniques like inlining, escape analysis, and virtual method resolution.

• JVM can inline methods by replacing the method call with the actual code, reducing overhead.

• Escape analysis helps JVM determine if objects can be allocated on the stack instead of the heap.

• Virtual method resolution optimizes method calls by caching the resolved method to avoid repeated lookups.

Java is a high-level, object-oriented programming language known for its portability and versatility.

• Java is platform-independent, meaning it can run on any device with a Java Virtual Machine (JVM)

• It is object-oriented, allowing for modular and reusable code

• Java is used for developing a wide range of applications, from web and mobile apps to enterprise systems

• Popular frameworks and libraries in Java include Spring, Hib

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.

• Abstract class can have constructors, member variables, and methods, while interface cannot.

• A class can implement multiple interfaces but can only extend one abstract class.

• Abstract classes are used to define a common behavior among subclasses, while interfaces are used to define a contract for classes to impl...read more

Abstract classes can have both implemented and abstract methods, while interfaces can only have abstract methods. Abstract classes support single inheritance, interfaces support multiple inheritance.

• Abstract classes can have both implemented and abstract methods, providing more flexibility in design.

• Interfaces can only have abstract methods, promoting a more strict contract for implementing classes.

• Abstract classes sup...read more