Java Stream API Coding Interview Questions on Integer Collections: When preparing for Java interviews, one of the most important topics for developers with 3–10 years of experience is the Stream API. The Stream API is not only used for data processing but also for solving real-world logical problems in an efficient, functional style.
In this post, we’ll explore 34 Java Stream API interview questions that focus only on integer collections. These questions are grouped into categories so you can understand the thought process behind solving them.
Blog 1: Top 10 Basic Stream API Logical Interview Questions on Integer Collections
In this post, we’ll start with the fundamentals of the Java Stream API using integer collections. These problems cover filtering, aggregation, and basic transformations, the building blocks of interview questions.
Questions Covered:
- Given a list of integers, find the maximum and minimum values.
- Find the second-highest and second-lowest numbers in a list.
- From a list, remove all duplicate numbers.
- Count how many times each number occurs in a list.
- Calculate the sum of all numbers in a collection.
- Find the average value from a list of numbers.
- Extract all numbers greater than 10 from a list.
- Sort a list of integers in both ascending and descending order.
- Merge two lists of integers into one, ensuring there are no duplicates.
- From a list of integers, separate even and odd numbers into two different results.
Answers: See Here
Blog 2: Intermediate Java Stream API Coding Problems for Interview Preparation
This post dives into intermediate-level problems that are commonly asked in interviews. You’ll see questions involving conditions, mathematical checks, and logical transformations with streams.
Questions Covered:
- From a list of integers, find all prime numbers.
- Extract the first 5 even numbers from a collection.
- Convert all integers in a list into their squared values.
- From a list, calculate the total of all even numbers.
- Check if every number in a list is positive.
- Verify whether any negative number exists in a collection.
- From a list, calculate the product of all numbers.
- Identify the number that occurs the most frequently in a collection.
- Divide a list of integers into two groups based on whether they are even or odd.
- From a list of integers, determine the nth largest element.
Answers: See Here
Blog 3: Advanced Java Stream API Logical Programs Frequently Asked in Interviews
This post takes things with complex interview-style problems. These questions often require a mix of filtering, sorting, and combining data — exactly the kind of logical problems mid-to-senior Java developers face in interviews.
Questions Covered:
- From a list, remove all numbers greater than 100.
- Given two lists of integers, find the numbers that are present in both.
- From two lists, identify numbers that appear in one list but not in the other.
- Reverse the order of elements in a list of integers.
- Given a sequence of numbers from 1 to N with one missing, find the missing number.
- Determine whether a list contains any duplicate values.
- From a list of integers, identify the longest consecutive sequence of numbers.
- Find all pairs of numbers in a list that add up to a specific target value.
Answers: See Here
Blog 4: Real-World Java Stream API Collector Problems on Integer Collections
In this final post, we’ll solve real-world problems using collectors, grouping, and partitioning. These problems are especially important because they reflect practical use cases in enterprise Java applications.
Questions Covered:
- From a list, find numbers that appear more than once.
- Group numbers into two categories: even and odd.
- From a collection, find the top three highest numbers.
- Convert a list of integers into a mapping where each number is associated with its square.
- Find the first number in a list that does not repeat.
- Verify whether a list of integers is sorted in ascending order.
All the above blog posts will be coming soon…Stay tuned.