AT&T Java Developer Interview Questions and Answers

Round duration - 15 minutes
Round difficulty - Easy

This was a group discussion round where we were divided into groups of 10 and we had 15 minutes for GD.

Round duration - 60 minutes
Round difficulty - Medium

This is all about how good you are with the fundamentals. Out of 10 I would give it a 6.5 on difficulty.

Q1. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from the end to the beginning and append each character to a new string.

• Use built-in functions like reverse() or StringBuilder in languages like Python or Java for efficient reversal.

• Handle special characters and numbers while reversing the string.

• Ensure to consider the constraints on the length of the string and the
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Q2. What is a deadlock?
Ans. 
A deadlock is a situation in which two or more processes are unable to proceed because each is waiting for the other to release a resource.
• Occurs in multitasking environments where processes compete for limited resources

• Can be resolved using techniques like deadlock prevention, deadlock avoidance, and deadlock detection

• Example: Process A holds Resource X and waits for Resource Y, while Process B holds Resource Y and wa
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Q3. What is a thread?
Ans. 
A thread is a lightweight sub-process that allows concurrent execution within a single process.
• Threads share the same memory space within a process.

• Threads are used to achieve parallelism and improve performance.

• Examples of threads include the main thread in a program and worker threads in a multi-threaded application.
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Q4. What is the difference between Multiprocessing and Multiprogramming?
Ans. 
Multiprocessing involves multiple processors executing multiple tasks simultaneously, while multiprogramming involves multiple programs sharing a single processor by switching between them.
• Multiprocessing utilizes multiple processors to execute multiple tasks concurrently.

• Multiprogramming involves multiple programs sharing a single processor by switching between them.

• Multiprocessing is more efficient in terms of perfor...read more
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Q5. Can you explain the process life cycle in an operating system?
Ans. 
Process life cycle in an operating system involves creation, execution, termination, and resource management.
• Creation: When a process is created, it is assigned a unique process ID and allocated necessary resources.

• Execution: The process is then scheduled by the operating system to run on the CPU.

• Termination: Once the process completes its task or is terminated by the user, it is removed from memory.

• Resource Management...read more
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Q6. What are the differences between Windows XP and Windows 7?
Ans. 
Windows XP and Windows 7 are both operating systems developed by Microsoft, but they have several key differences.
• User interface: Windows 7 has a more modern and user-friendly interface compared to Windows XP.

• Performance: Windows 7 is generally faster and more stable than Windows XP.

• Security: Windows 7 has more advanced security features and updates compared to Windows XP.

• Hardware support: Windows 7 supports newer hard...read more
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Round duration - 60 minutes
Round difficulty - Easy

Technical round with questions on DBMS and Networking mainly.

Q1. What is the difference between RDBMS and DBMS?
Ans. 
RDBMS is a type of DBMS that stores data in a structured format with relationships between tables.
• RDBMS enforces referential integrity and allows for normalization of data.

• DBMS is a general term for any system that manages databases, while RDBMS specifically refers to relational databases.

• Examples of RDBMS include MySQL, Oracle, and SQL Server.

• Examples of DBMS include MongoDB and Redis.
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Q2. What is an Object-Oriented Database Management System (OODBMS)?
Ans. 
An Object-Oriented Database Management System (OODBMS) is a type of database management system that supports the creation and management of objects in a database.
• OODBMS stores data in the form of objects, which can contain attributes and methods.

• It allows for complex data structures and relationships to be represented more easily.

• Examples of OODBMS include db4o, ObjectDB, and ObjectStore.
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Q3. How do you find the number of unique values in a SQL database?
Ans. 
Use the COUNT DISTINCT function in SQL to find the number of unique values in a database.
• Use the COUNT DISTINCT function along with the column name to count the number of unique values in that column.

• For example, SELECT COUNT(DISTINCT column_name) FROM table_name;

• You can also use GROUP BY to find the number of unique values for multiple columns.
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Q4. What is the difference between a hub and a switch in networking?
Ans. 
A hub operates at the physical layer and broadcasts data to all devices on the network, while a switch operates at the data link layer and forwards data only to the intended recipient.
• Hub operates at the physical layer, while switch operates at the data link layer

• Hub broadcasts data to all devices on the network, while switch forwards data only to the intended recipient

• Switch is more efficient and secure compared to a
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Q5. Can you explain the different OSI layers?
Ans. 
The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven different layers.
• Physical Layer: Deals with the physical connection between devices. Example: Ethernet cables.

• Data Link Layer: Responsible for node-to-node communication. Example: MAC addresses.

• Network Layer: Manages routing of data packets. Example: IP addresses.

• T...read more
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Q6. What are the different protocols supported at each OSI layer?
Ans. 
Different protocols supported at each OSI layer
• Layer 1 (Physical): Ethernet, Wi-Fi, Bluetooth

• Layer 2 (Data Link): MAC, PPP, HDLC

• Layer 3 (Network): IP, ICMP, ARP

• Layer 4 (Transport): TCP, UDP, SCTP

• Layer 5 (Session): NetBIOS, PPTP

• Layer 6 (Presentation): SSL, TLS

• Layer 7 (Application): HTTP, FTP, SMTP
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Round duration - 15 minutes
Round difficulty - Easy

IF you make it to the HR round you are selected. All 28 that attended got selected . It was more like stuff for formality. The usual questions.