IT Interview Questions Bank: Java, Python, SQL, Networking and Support

The short version

Do not memorise answers word for word. Understand the idea behind each question, then explain it in your own words with a small example. Interviewers can tell the difference.

Java

• Interface vs abstract class: an interface defines a contract, an abstract class can share state and code
• How HashMap works: keys are hashed to buckets and collisions are handled in the bucket
• String vs StringBuilder: strings are immutable, a builder is efficient for repeated changes
• Checked vs unchecked exceptions: checked ones must be handled or declared
• What is garbage collection: automatic release of unused objects

Python

• List vs tuple: a list is mutable, a tuple is not
• What are decorators: functions that wrap other functions to add behaviour
• What is a generator: a function that yields values lazily
• Shallow vs deep copy: whether nested objects are copied or shared
• What is a virtual environment: an isolated set of packages for a project

SQL

• Inner join vs left join: only matching rows vs all rows from the left plus matches
• WHERE vs HAVING: filters rows before vs after grouping
• What is an index: a structure that speeds up lookups at the cost of writes
• What is normalisation: organising data to reduce duplication
• Delete vs truncate vs drop: remove rows, remove all rows quickly, remove the table

Networking

• What is the difference between TCP and UDP?
• What is DNS and how does it work?
• What is a subnet mask?
• What happens when you type a URL in a browser?
• What is the difference between a switch and a router?

Support and troubleshooting

• How do you approach a problem you have never seen?
• A user cannot connect to Wi-Fi. What do you check?
• How do you handle an angry customer?
• When do you escalate a ticket?
• What is the difference between an incident and a service request?

How to use this bank

1. Pick your area and read each question aloud.
2. Answer without notes, then check yourself.
3. Add a tiny example or code snippet to each answer.
4. Mark weak topics and revise them first.
5. Practise with a friend who asks follow-up questions.

Next step

Revise one area a day for a week. Then register on JobKarle, complete your profile and apply.