30+ Oracle Associate Consultant Interview Questions and Answers

Program to remove duplicate elements from String and count their occurrences.

• Create a HashSet to store unique characters from the String.

• Iterate through the String and add each character to the HashSet.

• While adding, check if the character already exists in the HashSet and increment its count.

• Print the count of each character that has duplicates.

• Return the modified String with duplicates removed.

Marker interface is an interface with no methods. It is used to mark a class for special treatment.

• Marker interface is used to provide metadata to the JVM.

• It is used to indicate that a class has some special behavior or characteristics.

• Example: Serializable interface in Java.

• Marker interfaces are used for reflection and serialization.

• They are also used in frameworks like Spring and Hibernate.

• Marker interfaces are also known as tagging interfaces.

• They are used to group classes...read more

A program to capitalize the first letter of each word in a sentence.

• Split the sentence into words

• Loop through each word and capitalize the first letter

• Join the words back into a sentence

Remove strings from an array whose length is less than 3.

• Loop through the array and check the length of each string.

• If the length is less than 3, remove that string from the array.

• Use a for loop or filter method to remove the strings.

• Example: ['cat', 'dog', 'bird', 'elephant'] -> ['cat', 'dog', 'bird', 'elephant']

• Example: ['a', 'to', 'the', 'in'] -> ['the', 'in']

Lists are used for small collections, linked lists for large or frequently modified collections.

• Use lists for small collections that don't require frequent modifications.

• Use linked lists for large collections or collections that require frequent modifications.

• Linked lists are better for inserting or deleting elements in the middle of the collection.

• Lists are better for accessing elements by index.

• Example: Use a list to store a small list of names, use a linked list to impleme...read more

Microcontroller is a self-contained system with memory, peripherals and processor, while microprocessor only has a processor.

• Microcontroller has on-chip memory and peripherals, while microprocessor requires external memory and peripherals.

• Microcontroller is used in embedded systems, while microprocessor is used in general-purpose computing.

• Examples of microcontrollers include Arduino, PIC, and AVR, while examples of microprocessors include Intel Pentium, AMD Ryzen, and ARM Co...read more

Program to separate even and odd numbers using Java 8.

• Use Java 8 Stream API to filter even and odd numbers

• Create two separate lists for even and odd numbers

• Use lambda expressions to filter the numbers

• Example: List evenNumbers = numbers.stream().filter(n -> n % 2 == 0).collect(Collectors.toList());

• Example: List oddNumbers = numbers.stream().filter(n -> n % 2 != 0).collect(Collectors.toList());

Sensitive information can be removed from serializable interface by implementing custom serialization.

• Create a custom serialization method that excludes sensitive information.

• Use the transient keyword to mark sensitive fields as non-serializable.

• Consider using encryption or hashing to protect sensitive data.

• Test serialization and deserialization to ensure sensitive information is not included.

• Examples: exclude passwords, credit card numbers, and personal identification inform...read more

Yes, an array can have elements of different data types.

• An array can have elements of different data types, but it's not recommended.

• It can make the code harder to read and maintain.

• For example, an array can have both strings and numbers: ['apple', 5, 'banana']

Java Map is an interface that maps unique keys to values. It works internally using hash table data structure.

• Map interface is implemented by HashMap, TreeMap, LinkedHashMap, etc.

• Keys in a map must be unique and values can be duplicated.

• Hash table data structure is used to store key-value pairs internally.

• Hashing is used to convert keys into indices of an array where values are stored.

• Collision resolution techniques like chaining and open addressing are used to handle collisi...read more

A linked list is a linear data structure where each element is a separate object linked together by pointers.

• Linked list is used to implement stacks, queues, and hash tables.

• It is used in computer memory allocation.

• It is used in image processing to represent pixels.

• It is used in music player to create a playlist.

• It is used in web browsers to store the history of visited web pages.

Primitives are basic data types in Java while wrapper classes are objects that wrap around primitives.

• Primitives are faster and take less memory than wrapper classes.

• Wrapper classes provide additional functionality like conversion to and from strings.

• Primitives are passed by value while wrapper classes are passed by reference.

• Examples of primitives include int, boolean, and double while examples of wrapper classes include Integer, Boolean, and Double.

The OSI model has 7 layers that define how data is transmitted over a network.

• Layer 1: Physical layer - deals with the physical aspects of transmitting data

• Layer 2: Data link layer - responsible for error-free transfer of data between nodes

• Layer 3: Network layer - handles routing of data between different networks

• Layer 4: Transport layer - ensures reliable delivery of data between applications

• Layer 5: Session layer - establishes and manages connections between applications

• Lay...read more

Data structures are ways of organizing and storing data in a computer so that it can be accessed and used efficiently.

• Data structures can be linear or non-linear

• Examples of linear data structures include arrays, linked lists, and stacks

• Examples of non-linear data structures include trees and graphs

• Choosing the right data structure is important for optimizing performance and memory usage

TCP/IP model has four layers: Application, Transport, Internet, and Network Access.

• Application layer handles high-level protocols like HTTP, FTP, SMTP, etc.

• Transport layer provides end-to-end communication between hosts using TCP or UDP protocols.

• Internet layer handles the routing of data packets between networks using IP protocol.

• Network Access layer deals with the physical transmission of data over the network.

• Examples of protocols at each layer: HTTP (Application), TCP (Tr...read more

String Buffer and String Builder are both used to manipulate strings, but the former is synchronized while the latter is not.

• String Buffer is thread-safe while String Builder is not

• String Builder is faster than String Buffer

• String Builder is preferred when thread safety is not a concern

• String Buffer is used when multiple threads are involved in manipulating the same string

• Both classes have similar methods for appending, inserting, and deleting characters

Difference between @Service and @Component

• Both are used for component scanning in Spring

• @Service is used for service layer classes

• @Component is used for general purpose beans

• Service layer classes contain business logic

• Examples of @Service: UserService, ProductService

• Examples of @Component: DAO, Utility classes

TCP/IP model is a protocol used for data communication. It consists of four layers: application, transport, internet, and network access.

• Data is sent from the application layer to the transport layer where it is divided into segments.

• The internet layer adds IP addresses to the segments and sends them to the network access layer.

• The network access layer adds physical addresses and sends the data over the network.

• The process is reversed at the receiving end.

• Examples of TCP/IP p...read more

Transactions in a bank involve the movement of funds between accounts or the exchange of currency.

• Transactions can be initiated by customers or by the bank itself

• Common types of transactions include deposits, withdrawals, transfers, and loans

• Transactions are recorded in the bank's ledger and may be subject to fees or interest

• Electronic transactions have become increasingly popular, such as online banking and mobile payments

String is immutable while StringBuffer is mutable.

• String objects are constant and cannot be changed once created.

• StringBuffer objects are mutable and can be modified.

• StringBuffer is thread-safe while String is not.

• StringBuffer has methods to append, insert, and delete while String does not.

• Example: String str = "hello"; StringBuffer sb = new StringBuffer("world");

• str.concat("world"); // returns a new string "helloworld"

• sb.append("hello"); // modifies the existing StringBuffer...read more

TCP is a reliable, connection-oriented protocol. UDP is a connectionless protocol. TLS is a secure protocol for data encryption.

• TCP ensures reliable data transmission by establishing a connection between sender and receiver.

• UDP is faster but less reliable as it does not establish a connection before sending data.

• TLS provides secure communication by encrypting data and verifying the identity of the communicating parties.

• TCP and UDP are transport layer protocols while TLS is a ...read more

There are four types of HTTP requests in Spring Boot: GET, POST, PUT, and DELETE.

• GET: used to retrieve data from a server

• POST: used to submit data to a server

• PUT: used to update existing data on a server

• DELETE: used to delete data from a server

• These requests are handled by the @RequestMapping annotation in Spring Boot

Spring Boot annotations are used to simplify the development process. Some common annotations are @SpringBootApplication, @RestController, @Autowired, @GetMapping, @PostMapping, @Service, @Repository, @Component, etc.

• The @SpringBootApplication annotation is used to mark the main class of the application.

• The @RestController annotation is used to mark a class as a RESTful controller.

• The @Autowired annotation is used to inject dependencies.

• The @GetMapping and @PostMapping annota...read more

String is immutable because it cannot be changed once created.

• Immutable objects are safer to use in multi-threaded environments.

• String pool in Java is possible because of immutability.

• StringBuffer and StringBuilder are mutable alternatives to String.

Remove duplicate elements in an array.

• Create a new empty array.

• Loop through the original array and check if the element already exists in the new array.

• If it doesn't exist, add it to the new array.

• Return the new array without duplicates.

The four pillars of OOPS are encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: Bundling data and methods that operate on the data into a single unit. Example: Using private variables and public methods in a class.

• Inheritance: Allowing a new class to inherit properties and behavior from an existing class. Example: Creating a subclass that inherits from a superclass.

• Polymorphism: The ability to present the same interface for different data types. Example:...read more

Factory Design Pattern is used to create objects without exposing the creation logic to the client.

• It provides a way to delegate the object creation to a factory class.

• It helps in achieving loose coupling between classes.

• It is useful when we have a super class with multiple sub-classes and based on input, we need to return one of the sub-class.

• Examples include: java.util.Calendar, java.text.NumberFormat, java.nio.charset.Charset

HTTP response codes indicate the status of a web request. There are 5 categories of codes.

• 1xx - Informational

• 2xx - Success

• 3xx - Redirection

• 4xx - Client Error

• 5xx - Server Error

JVM is an abstract machine that executes Java bytecode. It consists of class loader, runtime data area, and execution engine.

• JVM stands for Java Virtual Machine.

• It is responsible for executing Java bytecode.

• JVM architecture consists of class loader, runtime data area, and execution engine.

• Class loader loads the class files into the memory.

• Runtime data area is divided into method area, heap, and stack.

• Execution engine executes the bytecode.

• JVM provides platform independence to...read more

Functional interfaces are interfaces with only one abstract method. There are four types of functional interfaces.

• Consumer: accepts a single argument and returns no result. Example: Consumer

• Supplier: takes no argument and returns a result. Example: Supplier

• Predicate: takes a single argument and returns a boolean. Example: Predicate

• Function: takes a single argument and returns a result. Example: Function

PLSQL packages can be written in different ways. Here are some pointers.

• Packages can be written in a single file or multiple files.

• Procedures and functions can be written inside the package or outside the package.

• Packages can be created using CREATE PACKAGE statement or CREATE OR REPLACE PACKAGE statement.

• Packages can be compiled in debug mode using the keyword 'DEBUG'.

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

• Lambda expressions allow for functional programming and simplify code.

• Streams provide a way to process collections of data in a functional way.

• Default methods allow for adding new methods to interfaces without breaking existing implementations.

• Other features include the Optional class, Date and Time API, and Nashorn JavaScript engine.

• Example: Lambda expression - (x, y) -> x + y

• Ex...read more

SIP signalling is a protocol used for initiating, modifying, and terminating real-time sessions that involve video, voice, messaging, and other communications applications.

• SIP stands for Session Initiation Protocol.

• It is used to establish, modify, and terminate multimedia sessions.

• SIP signalling is used in VoIP (Voice over Internet Protocol) and other real-time communication applications.

• It uses a request-response model, where a client sends a request to a server and the serv...read more

Triggers are database objects that are used to automatically execute a set of actions when a specific event occurs.

• Triggers can be of two types: DML triggers and DDL triggers.

• DML triggers are fired in response to DML (Data Manipulation Language) events like INSERT, UPDATE, and DELETE.

• DDL triggers are fired in response to DDL (Data Definition Language) events like CREATE, ALTER, and DROP.

• Triggers are important as they help in maintaining data integrity, enforcing business rule...read more