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10: Find all permutations of a given string – Iteration in Java

Q. Complete the method “Set getAllCombinations(String input) ” where input is any string and the method should return all possible combinations of a given string.


import java.util.Collection;
import java.util.Collections;
import

…

10: Part-3: Java Tree structure interview and coding questions

This is an extension to Java Tree structure interview and coding questions — Part 2, and adds functional programming and recursion. Step 1: The Tree interface with get( ) method that …

10: What is wrong with this code? ConcurrentHashMap & Atomic operations

Q. What output is expected from the following code? What does it actually output?


import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public final

…

11: Part 4: Java Tree structure interview and coding questions

This is an extension to Java Tree structure interview questions and coding questions — Part 3 where recursion was used for FlattenTree interface. Let’s use iteration here. Step 1: The FlattenTree interface.

package

…

11: Threads performing tasks by talking to each other

Q. Given the following code


public class WorkingOnXandY {

    public static void main(String[] args) {
        SharedObject obj = new SharedObject();

        Thread thread1 = new Thread(new Runnable() {
            @Override
            public

…

12: Complete the trades matching logic

Q. Given the following code


import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class TradeMatcher {

    private final Scanner in;
    private final BufferedWriter out;

    public

…

13: Atomicity, Visibility, & synchronization in Java

Q. Given the following code, Client


package com.homeassignment.task5;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.LockSupport;

public class Client {

    private AtomicInteger requestCount = new AtomicInteger(0);

…

2. Implement an in-memory LRU cache in Java with TTL

Q: Implement an in-memory cache in Java without using any frameworks. The basic requirements are – The TTL (Time To Live) for the cache items are ~10 seconds [just for …

20 Java coding interview questions – tips & considerations

Java coding interview questions are very common in job interviews. Good coding skills are essentials for passing the peer code reviews with flying colours. Here are 17 coding tips with …

3. Multi-Threading – Create a simple framework where work items can be submitted

Q: Create a simple framework where work items can be submitted using Java 8 or later. Here are the use cases: #1: A work item is an instance of a …

4a. 10-digit phone number to produce a list of words matching first letters of the phone number

Q: Write a program that takes any 10-digit phone number and produces a list of words matching first letters of the phone number (2 – ABC, 3 – DEF, .. …

4b. FP approach 10-digit phone number to produce a list of words matching first letters of the phone number

This makes use of the Functional Programming (FP) approach. Q: Write a program that takes any 10-digit phone number and produces a list of words matching first letters of the …

5a – Writing a simple SQL where clause parser in Java – Part 1

Problem Statement: How would you go about writing an SQL WHERE clause parser to evaluate a given condition against the given data in a Hashmap. For example:

public class ParserTest

…

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About
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Arulkumaran Kumaraswamipillai

In 1999, I transformed my career from a Mechanical engineer to a self-taught Java engineer within 1 year, and a Java freelancer within 2 years, and in 2016 to a self-taught Big Data freelancer.

Over the past 22+ years, I have built a high-demand career as a Java & Big Data freelancer, delivering mission-critical solutions for 13+ top-tier organisations with a proven track record that has generated over 130+ job offers to choose from 150+ job interviews.

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Email: java-interview@hotmail.com

Latest posts by Arulkumaran Kumaraswamipillai (see all)

How would you go about.. building an ETL pipeline to handle 3k TPS (i.e transactions per second) - April 17, 2026
00b: Python variable scopes, assigning types optionally and execution order interview Q&As - April 11, 2026
How to prepare for the Java job interviews? - January 3, 2026

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Blog Archives

10: Find all permutations of a given string – Iteration in Java

10: Part-3: Java Tree structure interview and coding questions

10: What is wrong with this code? ConcurrentHashMap & Atomic operations

11: Part 4: Java Tree structure interview and coding questions

11: Threads performing tasks by talking to each other

12: Complete the trades matching logic

13: Atomicity, Visibility, & synchronization in Java

2. Implement an in-memory LRU cache in Java with TTL

20 Java coding interview questions – tips & considerations

3. Multi-Threading – Create a simple framework where work items can be submitted

4a. 10-digit phone number to produce a list of words matching first letters of the phone number

4b. FP approach 10-digit phone number to produce a list of words matching first letters of the phone number

5a – Writing a simple SQL where clause parser in Java – Part 1

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