NeoSOFT Java Developer Interview Questions and Answers

ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list.

• ArrayList provides fast random access and slower insertion/deletion, while LinkedList provides fast insertion/deletion and slower random access.

• ArrayList uses less memory overhead compared to LinkedList.

• Example: ArrayList is more suitable for scenarios where frequent access and traversal of elements is required, ...read more

HashMap is not thread-safe, while ConcurrentHashMap is designed for concurrent access, allowing safe multi-threaded operations.

• HashMap allows null keys and values; ConcurrentHashMap does not allow null keys or values.

• HashMap is not synchronized, leading to potential data inconsistency in multi-threaded environments.

• ConcurrentHashMap uses a segmented locking mechanism, allowing multiple threads to read and write co...read more

HashSet is an unordered collection while TreeSet is a sorted collection.

• HashSet uses hashing to store elements, allowing for constant time complexity for basic operations like add, remove, and contains.

• TreeSet uses a Red-Black tree to store elements in sorted order, allowing for log(n) time complexity for basic operations.

• HashSet does not maintain any order of elements while TreeSet maintains elements in sorted or...read more

Hash map is a data structure that stores key-value pairs and allows for fast retrieval of values based on keys.

• Hash map uses hashing to map keys to their corresponding values.

• It allows for constant time complexity O(1) for insertion, deletion, and retrieval operations.

• Example: HashMap<String, Integer> map = new HashMap<>(); map.put("key", 123); int value = map.get("key");

Entity class represents a table in a database and its attributes as fields.

• Define class with @Entity annotation

• Add @Id annotation to primary key field

• Add @Column annotation to map fields to table columns

• Implement getters and setters

• Override equals() and hashCode() methods

Circuit breaker is a design pattern used to prevent cascading failures in distributed systems. Hystrix is a popular implementation.

• Circuit breaker monitors the availability of a service and trips if the service fails repeatedly.

• It helps to prevent cascading failures by failing fast and providing fallback options.

• Hystrix is a popular implementation of circuit breaker pattern in Java.

• It provides features like reques...read more