Zocket Technologies Interview Questions and Answers

Identify all prime numbers less than or equal to a given positive integer N.

• Iterate from 2 to N and check if each number is prime

• Use the Sieve of Eratosthenes algorithm for better efficiency

• Optimize by only checking up to the square root of N for divisors

Check if a given string is a palindrome after removing special characters, spaces, and converting to lowercase.

• Remove special characters and spaces from the string

• Convert the string to lowercase

• Check if the modified string is a palindrome by comparing characters from start and end

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 with implementation.

• Interface can only have abstract methods and constants.

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

• Example: Abstract class - Animal with abstract method 'eat', Interface - Flyable with method 'fly'.

Error is a serious issue that cannot be handled at runtime, while Exception is a recoverable issue that can be caught and handled.

• Error is a subclass of Throwable and is usually caused by the environment or system, such as running out of memory or stack overflow.

• Exception is also a subclass of Throwable but is caused by the application code, such as invalid input or file not found.

• Errors are unchecked and are not meant to be caught or handled by the application, while Excepti...read more

Requirements for creating an immutable class in Java

• Make the class final so it cannot be extended

• Make all fields private and final

• Do not provide setter methods, only getter methods

• Ensure that mutable objects are not returned in getter methods

• Override equals() and hashCode() methods for proper comparison

• Consider making defensive copies of mutable fields in constructor or getter methods

Static methods belong to the class itself, while instance methods belong to individual objects of the class.

• Static methods are called using the class name, while instance methods are called using object references.

• Static methods cannot access instance variables directly, while instance methods can access both static and instance variables.

• Static methods are shared among all instances of the class, while instance methods are unique to each object.

• Example: Math.max() is a stati...read more

ClassNotFoundException occurs when a class is not found during runtime, while NoClassDefFoundError occurs when a class was found during compilation but not during runtime.

• ClassNotFoundException is a checked exception, while NoClassDefFoundError is an Error.

• ClassNotFoundException occurs when a class is not found at runtime, usually due to a missing classpath or incorrect class name.

• NoClassDefFoundError occurs when a class was found during compilation but not found during runti...read more