Java Lead Interview Questions and Answers

Customized collections in Java can be created by implementing the Collection interface or extending existing collection classes.

• Implement the Collection interface and provide custom implementations for methods like add, remove, contains, etc.

• Extend existing collection classes like ArrayList or LinkedList and override methods as needed.

• Consider using generics to ensure type safety and reusability of the customized collection.

This task involves counting the frequency of each character in a given string using Java.

• Use a HashMap to store characters as keys and their frequencies as values.

• Iterate through the string, updating the count for each character.

• Example: For the string 'hello', the output should be {h=1, e=1, l=2, o=1}.

• Consider edge cases like empty strings or strings with special characters.

Find the longest palindrome in an array of strings using Java 8 streams.

• Use Java 8 streams to filter palindromes from the array.

• Define a palindrome check method to verify if a string reads the same forwards and backwards.

• Use the 'max' method with a custom comparator to find the longest palindrome.

• Example: For input ['racecar', 'hello', 'level'], the output should be 'racecar'.

Code to find anagram strings in an array of strings

• Iterate through the array of strings

• Sort each string alphabetically

• Store sorted strings in a hashmap with original string as key

• Return values of hashmap as list of anagram strings

Yes, I have used Aspect-Oriented Programming (AOP) in Java for cross-cutting concerns like logging and transaction management.

• AOP allows separation of cross-cutting concerns from business logic.

• Common use cases include logging, security, and transaction management.

• In Spring, AOP is implemented using annotations like @Aspect and @Before.

• Example: Using @Around to log method execution time.

• AOP can improve code maintainability and readability.

Throttling in REST API is a technique used to limit the number of requests a client can make within a certain timeframe.

• Throttling helps prevent server overload and ensures fair usage of resources.

• Common methods of throttling include rate limiting, concurrency limiting, and request queuing.

• For example, setting a rate limit of 100 requests per minute for a specific endpoint.

• Throttling can be implemented at the API gateway level or within the application code.

Java 8 introduced several new features including lambda expressions, streams, functional interfaces, and default methods.

• Lambda expressions allow you to write more concise code by providing a way to pass functions as arguments.

• Streams provide a new way to work with collections in a functional style, allowing for easier parallel processing.

• Functional interfaces are interfaces with a single abstract method, which can be implemented using lambda expressions.

• Default methods allow...read more

Invariants in Java are conditions that must always be true at a certain point in a program's execution.

• Invariants help ensure the correctness of a program by defining conditions that should always hold true.

• They are typically used in loops, data structures, and class invariants.

• For example, in a stack data structure, an invariant could be that the stack is never empty when popping an element.