Oracle Associate Consultant Interview Questions, Process, and Tips

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...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

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 password...read more

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 ...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

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.chars

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

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

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 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 - e...read more

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.

• Exampl...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...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 mode...read more

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 pro...read more

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']