Code Snippets
Tutorials, guides, and interview prep for QA automation engineers.
Pattern Matching in Strings Java | Regex & KMP Algorithm
Learn how to perform pattern matching in Java using indexOf(), Regular Expressions, and the KMP algorithm. Explore code examples, FAQs, and the best approach for tex
String Compression in Java | RLE Compression Technique
Learn how to implement string compression in Java using Run-Length Encoding (RLE). Explore compression and decompression code examples, outputs, FAQs, and performanc
Sort Words Alphabetically Java | Complete Guide
Learn how to sort words in alphabetical order in Java using Arrays.sort(), case-insensitive sorting, and Streams. Explore code examples, output, FAQs, and the best s
Count Character Frequency in String Java | Complete Analysis
Learn how to count character frequency in a Java string using HashMap, Streams, and a character array. Explore code examples, FAQs, and the best methods.
Remove Duplicate Words from Sentence Java | 2 Methods
Learn how to remove duplicate words from a sentence in Java using LinkedHashSet and Streams. Explore code examples, output, FAQs, and the best approach for text clea
Count Word Frequency in Sentence Java | HashMap Guide
Learn how to count the frequency of each word in Java using HashMap, LinkedHashMap, and Streams. Explore code examples, output, FAQs, and the best approach for text
Find Shortest Word in Sentence Java | Quick Guide
Learn how to find the shortest word in a sentence in Java using a loop, Streams, and Collections.min(). Explore code examples, FAQs, and the best approach for text a
Reverse Word Order in Sentence Java | 3 Methods Explained
Learn how to reverse the order of words in a sentence in Java using Collections.reverse(), Streams, and Stack. Explore step-by-step examples, source code, outputs, F
Reverse Each Word in Sentence Java | Step-by-Step Guide
Learn how to Reverse Each Word in Sentence Java step by step with code snippets, FAQs.
Count Words in Sentence Java | 4 Methods with Code Examples
Learn how to count words in a sentence in Java using split(), StringTokenizer, regex, Streams, and manual iteration. Includes examples, performance comparison.
Swap Two Characters in String Java | 3 Methods Explained
Swap Two Characters in String Java with all 3 Methods Explained
Check if String Contains Only Alphabets Java | Multiple Methods
Check if String Contains Only Alphabets Java with Multiple Methods explained
Check if String Contains Only Digits Java | Multiple Methods
Check if String Contains Only Digits Java
Remove Duplicate Characters from String Java | 4 Methods
Introduction Removing duplicate characters from a string is a common string manipulation problem in Java. It frequently appears in technical interviews, coding challenges, and real-world applications
Find Duplicate Characters in String Java | 4 Methods Explained
Find Duplicate Characters in String Java
Count Digits Letters Spaces Special Characters Java | Complete Guide
Count Digits Letters Spaces Special Characters Java
Check if Strings are Anagrams Java | 4 Methods Explained
Check if Strings are Anagrams Jav
Replace Character in String Java | replace() and replaceAll() Methods
Replace Character in String Java
Remove Whitespaces from String Java
remove whitespaces from string Java
Concatenate Strings Without + Operator in Java | 5 Methods Explained
Concatenate Strings Without + Operator in Java | learn all different 5 Methods Explained.
Find String Length Without length() Method in Java | Alternative Methods
Learn alternative methods to find string length without using length() method, including loops, arrays, and stream approaches.
Count Characters in a String Java | length() Method Explained
Learn how to count characters in Java strings using length() method, with examples for counting specific types of characters and handling edge cases.
Convert String to Uppercase and Lowercase in Java | Complete Guide
Learn how to convert strings to uppercase and lowercase in Java using toUpperCase() and toLowerCase() methods with code examples.
Compare Strings in Java | Case Sensitive & Insensitive Methods Explained
Learn how to compare strings in Java with case sensitivity options. Includes equals(), compareTo(), and regionMatches() methods with code examples.
Java Palindrome Check | 4 Methods with Code Examples & Best Practices
Learn 4 different methods to check if a string is a palindrome in Java. Includes code examples, best practices, and performance analysis for interviews.
How to Reverse a String in Java | 5 Best Methods
Learn 5 different ways to reverse a string in Java with code examples, performance analysis, and detailed explanations for
Verify Number Is Palindrome in Java: A QA Testing Approach
Learn how to verify a palindrome number in Java using JUnit assertions and proper test case design, covering boundary values and edge cases, with FAQs.
Find Missing Number in a Sequence in Java: 4 Methods (2026)
Learn how to find a missing number in a sequence in Java using the sum formula, XOR, and HashSet, plus how to find multiple missing numbers, with FAQs.
Find Duplicate Numbers in an Array in Java: 4 Methods (2026)
Learn how to find duplicate numbers in a Java array using brute force, sorting, HashSet, and Streams, with time complexity comparisons and FAQs.
Sum of Numeric Digits in a String in Java: Full Guide (2026)
Learn how to sum numeric digits in a Java string — both individual digit characters and complete embedded numbers — with full code and FAQs.
Compare Two Numeric Values From Strings in Java (2026)
Learn why comparing numbers as strings in Java produces wrong results, and how to correctly compare numeric string values by parsing them first, with FAQs
Generate Random Number in Java: Random, Math.random & More
Learn how to generate random numbers in Java using Math.random, java.util.Random, ThreadLocalRandom, and SecureRandom, with ranges, seeds, and FAQs.
Validate Number in Range in Java: Inclusive vs Exclusive (2026)
Learn how to validate whether a number falls within a range in Java, covering inclusive vs exclusive boundaries, user input, and common off-by-one bugs.
Extract Numeric Part From a String in Java: 4 Methods (2026)
Learn how to extract numeric parts from alphanumeric strings in Java using regex, StringBuilder, and replaceAll, with practical examples and FAQs.
Count Numeric Values in a String in Java: Full Guide (2026)
Learn how to count numeric values (not just digit characters) in a Java string using regex Matcher and manual parsing, with full code and FAQs.
Count Digits, Letters, Spaces & Special Chars in Java (2026)
Learn how to count digits, letters, spaces, and special characters in a string using Java's Character class methods, with full code and FAQs.
Check If a Number Is Binary or Not in Java (2026 Guide)
Learn how to check if a number is binary in Java using a while loop and regular expressions, covering both int and String inputs, with FAQs.
Check Buzz Number in Java: Divisibility + Last Digit (2026)
Learn how to check Buzz numbers in Java by testing divisibility by 7 or a last digit of 7, with full code, examples, and interview FAQs.
Check Magic Number in Java: Digit Sum Reduction (2026)
Learn how to check magic numbers in Java by repeatedly summing digits until reaching a single digit and checking if it equals 1, with FAQs.
Check Automorphic Number in Java: Logic + Full Code (2026)
Learn how to check automorphic numbers in Java by verifying if a number's square ends with the number itself, with numeric and String methods, plus FAQs.
Check Spy Number in Java: Sum vs Product of Digits (2026)
Learn how to check spy numbers in Java by comparing the sum and product of digits, with full code, examples, and interview FAQs.
Check Harshad Number in Java: Logic + Full Code (2026)
Learn how to check Harshad (Niven) numbers in Java by testing divisibility by the digit sum, with full code, examples, and interview FAQs.
Check Happy Number in Java: Logic + Cycle Detection (2026)
Learn how to check happy numbers in Java using sum of squared digits, with HashSet-based and Floyd's cycle detection to avoid infinite loops, plus FAQs.
Calculate Compound Interest in Java: Formula + Full Code (2026)
Learn how to calculate compound interest in Java using Math.pow, with support for different compounding frequencies, year-by-year breakdowns, and FAQs.
Calculate Simple Interest in Java: Formula + Full Code (2026)
Learn how to calculate simple interest in Java using the standard formula, with user input via Scanner, correct decimal formatting, and FAQs.
Convert Binary to Decimal in Java: 4 Methods Explained (2026)
Learn how to convert binary numbers to decimal in Java using a while loop, recursion, and Integer.parseInt, with positional notation explained and FAQs.
Convert Decimal to Binary in Java: 4 Methods Explained (2026)
Learn how to convert decimal numbers to binary in Java using a while loop, recursion, StringBuilder, and Integer.toBinaryString, with FAQs and examples.
Find Smallest and Largest Digit in a Number in Java (2026)
Learn how to find the smallest and largest digit in a number using Java, with a while loop, Math.max/min, recursion, and negative number handling.
Print Numbers Without Loop in Java: Recursion (1 to N & N to 1)
Learn how to print numbers from 1 to N and N to 1 in Java without using any loop, using pure recursion, with clear call-stack traces and FAQs.
Reverse a Number Without Loop in Java: Using Recursion (2026)
Learn how to reverse a number in Java without using any loop, relying purely on recursion, with a clean return-based design and interview FAQs.
Check Neon Number in Java: Logic + Full Code Explained (2026)
Learn how to check neon numbers in Java by squaring the number and summing the digits of the result, with full code, examples, and FAQs.
Sum of First N Natural Numbers in Java: Loop vs Formula
Learn how to find the sum of the first N natural numbers in Java using a loop, recursion, and the efficient Gauss formula, with FAQs and examples.
Palindrome Numbers in a Range in Java: Efficient Code (2026)
Learn how to find all palindrome numbers within a given range in Java using a reusable method, Streams, and an approach to find the largest one, with FAQs.
Armstrong Numbers in a Range in Java: Efficient Code (2026)
Learn how to find and print all Armstrong numbers within a given range in Java, using a reusable, efficient digit-count-aware method, with FAQs.
Find Factors of a Number in Java: Brute Force vs Optimized
Learn how to find and print all factors of a number in Java using brute force and the square-root-optimized method, with sorted output and FAQs.
Find LCM of Two Numbers in Java: Using GCD (Efficient Method)
Learn how to find the LCM of two numbers in Java using brute force and the efficient GCD-based formula, with code, math explanation, and FAQs.
Find GCD (HCF) of Two Numbers in Java: Euclidean Algorithm
Learn how to find the GCD (HCF) of two numbers in Java using brute force and the efficient Euclidean algorithm, with recursion, code, and FAQs.
Sum of Even and Odd Numbers in Java: Array & Range Methods
Learn how to find the sum of even and odd numbers in Java using loops, arrays, and Java Streams, plus mathematical shortcut formulas, with FAQs.
Print Fibonacci Series in Java: Loop, Recursion & Memoization
Learn to print the Fibonacci series in Java using a loop, naive recursion, and memoization — with time complexity comparisons and interview FAQs.
Check Strong Number in Java: Logic + Full Code Explained (2026)
Learn how to check strong numbers in Java by summing the factorial of each digit, with full code, step-by-step traces, and interview FAQs.
Check Perfect Number in Java: Logic, Code & Optimized Method
Learn how to check perfect numbers in Java using proper divisors, with a brute-force and square-root-optimized approach, plus FAQs and examples.
Check Armstrong Number in Java: Full Logic + Code (2026)
Learn how to check Armstrong numbers in Java for 3-digit and n-digit numbers, print Armstrong numbers in a range, and avoid common mistakes, with FAQs.
Check Palindrome Number in Java: Full Code + Logic (2026)
Learn how to check if a number is a palindrome in Java using a while loop, recursion, and StringBuilder — with full code, traces, and interview FAQs.
Check Prime Number in Java: Optimized Code (sqrt(n) Method)
Learn how to check if a number is prime in Java using brute force and the optimized square-root method, plus how to print primes in a range with FAQs.
Check Leap Year in Java: Simple Logic + Full Code (2026)
Learn the exact leap year rule and how to check leap year in Java using if-else and ternary operators, including the century-year exception, with FAQs.
Find Power of a Number in Java: Loop, Math.pow() & Recursion
Learn how to calculate the power of a number in Java using a loop, Math.pow(), recursion, and fast exponentiation — with code, output, and FAQs.
Find Factorial of a Number in Java: Loop, Recursion & BigInteger
Learn how to find the factorial of a number in Java using a for loop, while loop, recursion, and BigInteger for large numbers — with code and FAQs.
Count Number of Digits in Java: 4 Methods (Loop, String, Log10)
Learn 4 ways to count the number of digits in an integer in Java — while loop, String.length(), Math.log10(), and recursion — with code and FAQs.
Sum of Digits in Java: While Loop, Recursion & Optimized Code
Learn how to find the sum of digits of a number in Java using a while loop and recursion, including how to reduce it to a single digit (digital root).
Reverse a Number in Java: 4 Methods (Loop, Recursion, StringBuilder)
Learn to reverse a number in Java using a while loop, recursion, and StringBuilder. Includes step-by-step traces, output, and common interview mistakes.
Find the Largest Among 3 Numbers in Java (4 Methods + Code)
Learn how to find the largest of three numbers in Java using if-else, nested if, Math.max, and ternary operators. Includes code, output, and FAQs.
Swap Two Numbers in Java: With and Without a Third Variable (2026 Guide)
Learn to swap two numbers in Java using a temp variable, arithmetic operators, and XOR — with code, output, memory explanation, and interview tips.
Check Positive, Negative, or Zero in Java (Code + Interview Answer)
Step-by-step Java program to check if a number is positive, negative, or zero. Includes if-else logic, ternary version, memory explanation, and FAQs.
How to Check Even or Odd Number in Java (5 Easy Methods + Code)
Learn how to check even or odd numbers in Java using modulus, bitwise, and ternary operators. Includes code, output, interview answers, and common mistakes.
Display Upper and Lower Triangular Matrix Elements in Java
Learn how to display the upper and lower triangular elements of a matrix in Java, with correct index conditions and full code examples.
Check if a Matrix Is an Identity Matrix in Java (Full Guide)
Learn how to check whether a matrix is an identity matrix in Java, verifying both the diagonal and off-diagonal elements correctly.
Multiply Two Matrices in Java (Full Guide With Dimension Rules)
Learn how to multiply two matrices in Java using triple nested loops, understand dimension compatibility rules, and avoid common mistakes
Find the Sum of Diagonal Elements of a Matrix in Java (Both Diagonals)
Learn how to find the sum of both diagonals in a Java matrix, avoiding the classic double-counting bug for odd-sized matrices.
Print Diagonal Elements of a Matrix in Java (Both Diagonals)
Learn how to print the main and anti-diagonal elements of a matrix in Java, with the index formulas explained clearly for each.
Find the Transpose of a Matrix in Java (In-Place & New Matrix Methods)
Learn how to find the transpose of a matrix in Java for both square and non-square matrices, including the in-place swap technique.
Find Sum of Each Column in 2D Array in Java
Learn how to calculate the sum of each column in a Java 2D array using nested loops with swapped iteration order, and streams.
Find the Sum of Each Row in a 2D Array in Java (Step-by-Step)
Learn how to calculate the sum of each row in a Java 2D array using nested loops and streams, with full code examples and jagged array support.
Find the Sum of All Elements in a 2D Array in Java
Learn how to calculate the sum of all elements in a Java 2D array using nested loops and streams, including jagged array handling.
Create and Print a 2D Array in Java (Complete Beginner Guide)
Learn how to create, initialize, and print a 2D array in Java using nested loops and Arrays.deepToString(), including jagged arrays.
Convert an ArrayList to an Array in Java (toArray() Fully Explained)
Learn how to convert an ArrayList to an array in Java using toArray(), the zero-length array idiom, and streams, with full examples
Convert an Array to an ArrayList in Java
Learn every way to convert an array to an ArrayList in Java, including the Arrays.asList() trap and primitive array gotchas
Print an Array in Reverse Order Without Reversing It in Java
Learn how to print a Java array in reverse order without modifying the original array, using loops, streams, and ListIterator.
Find the Majority Element in a Java Array (Boyer-Moore Voting)
Learn how to find the majority element (appearing more than n/2 times) in a Java array using the Boyer-Moore Voting Algorithm, O(1) space
Check if an Array Is Sorted or Not in Java (Ascending & Descending)
Learn how to check if a Java array is sorted in ascending or descending order using a single pass loop, with full code and edge cases
Find a Pair with a Given Sum in a Java Array (Two Sum, O(n) Solution)
Learn how to find a pair of elements summing to a target value in a Java array using HashSet and two-pointer techniques, with full code.
Remove a Specific Element from an Array in Java
Learn how to remove a specific element from a Java array by value or index, using the shift technique and ArrayList conversion.
Find the Missing Number in an Array (1 to n) in Java
Learn to find the missing number in a 1-to-n array in Java using the sum formula, XOR trick, and boolean tracking, with full explanations
Move All Negative Numbers to the Beginning of a Java Array
Learn to move all negative numbers to the beginning of a Java array using two-pointer partitioning, with order-preserving and non-preserving methods
Move All Zeros to the Beginning of an Array in Java
Learn how to move all zeros to the beginning of a Java array in-place using a reverse two-pointer technique, with full code examples.
Move All Zeros to the End of an Array in Java
Learn how to move all zeros to the end of a Java array in-place using the two-pointer technique, preserving the order of non-zero elements
Find the Index of an Element in a Java Array (Linear & Binary Search)
Learn how to find the index of an element in a Java array using linear search, binary search, and streams, with complexity comparisons.
Rotate an Array to the Right in Java (Reversal Algorithm Guide)
Learn how to rotate a Java array to the right by k positions using the reversal algorithm and extra array method, with full examples
Rotate an Array to the Left in Java
Learn how to rotate a Java array to the left by k positions using extra array, juggling algorithm, and reversal techniques
Swap Two Elements in a Java Array (Temp Variable & XOR Methods)
Learn how to swap two elements in a Java array using a temp variable, arithmetic, and XOR, with clear explanations of why each works.
Replace an Element at a Specific Index in a Java Array
Learn how to replace an element at a specific index in a Java array safely, with validation, examples, and common mistakes to avoid.
Find Element at a Specific Index in a Java Array (Beginner Guide)
Learn how to access an array element at a specific index in Java, handle out-of-bounds errors safely, and understand zero-based indexing
Find Common Elements Between Two Arrays in Java (HashSet Method)
Learn how to find common elements between two arrays in Java using HashSet, retainAll(), and nested loops, with complexity comparisons.
Copy One Array to Another in Java (Shallow vs Deep Copy Explained)
Learn every way to copy an array in Java — clone(), Arrays.copyOf(), System.arraycopy() — and the crucial shallow vs deep copy distinction.
Merge Two Arrays in Java (With and Without Sorting)
Learn how to merge two arrays in Java using System.arraycopy(), manual loops, and streams, including sorted-merge techniques.
Compare Two Arrays for Equality in Java (Arrays.equals() & Beyond)
Learn how to check if two arrays are equal in Java using Arrays.equals(), deepEquals(), and manual loops, including order-sensitive cases.
Find Sum of Even and Odd Elements Separately in a Java Array
Learn to calculate the sum of even and odd elements separately in a Java array using loops and streams, with full code examples.
Count Positive and Negative Numbers in a Java Array (Complete Guide)
Learn how to count positive, negative, and zero values in a Java array using loops and streams, including the zero classification rule.
Separate Even and Odd Elements into Two Arrays in Java
Learn how to split a Java array into separate even and odd element arrays using two-pass counting and dynamic ArrayList methods.
Count Even and Odd Elements in a Java Array
Learn how to count even and odd elements in a Java array using the modulo operator, with negative number handling and streams.
Find the First Duplicate Element in a Java Array
Learn how to find the first duplicate element in a Java array in a single pass with HashSet, including the "first by index" nuance
Find Unique Elements in an Array in Java
Learn how to find elements that appear exactly once in a Java array using HashMap, LinkedHashSet, and the XOR trick for special cases
Count Frequency of Each Element in an Array in Java (HashMap Guide)
Learn how to count the frequency of each element in a Java array using HashMap, streams, and sorting-based approaches, with examples.
Remove Duplicates from an Array in Java
Learn how to remove duplicate elements from a Java array using LinkedHashSet, two pointers, and streams while preserving order.
Find Duplicate Elements in an Array in Java
Learn how to find duplicate elements in a Java array using nested loops, HashSet, and streams, with complexity analysis and real examples.
Reverse an Array in Java (In-Place, Recursive & Stream Methods)
Learn how to reverse an array in Java in-place, recursively, and with streams, complete with memory diagrams, examples, and best practices.
Sort an Array in Descending Order in Java (3 Practical Methods)
Learn how to sort an array in descending order in Java using manual loops, Collections.reverseOrder(), and streams, with full examples.
Sort an Array in Ascending Order in Java
Learn how to sort an array in ascending order in Java using bubble sort, Arrays.sort(), and streams, with complexity analysis and examples.
Find the Difference Between Max and Min in a Java Array
Learn to calculate the range (max minus min) of a Java array in a single pass, with code, memory diagrams, and real-world uses.
Find Second Smallest Element in an Array in Java
Learn to find the second smallest element in a Java array in one pass without sorting, including duplicate handling and edge cases.
Find Second Largest Element in an Array in Java
Learn how to find the second largest element in a Java array in a single pass without sorting, with edge cases and interview tips.
Find Minimum Element in an Array in Java
Learn to find the minimum element in a Java array with loops, streams, and Collections, including memory diagrams and common mistakes.
Find Maximum Element in Array in Java
Learn how to find the maximum element in a Java array using loops, Arrays.sort(), Collections, and streams, with full explanations.
Find Average of Array Elements in Java
Learn to calculate the average of array elements in Java, why type casting to double matters, and how to avoid the integer division trap.
Find Sum of Array Elements in Java
Learn how to calculate the sum of array elements in Java using for loops, enhanced loops, and streams, with memory diagrams and best practices.
How to Take Array Input From User in Java
Learn how to accept dynamic array input from users in Java with Scanner, including size validation, loops, and common pitfalls to avoid.
How to Find the Length of an Array in Java
Learn how the .length property works for Java arrays, how it differs from .length() for Strings, plus common pitfalls and best practices.
Print All Elements of an Array in Java (5 Easy Methods, 2026)
Discover 5 practical ways to print array elements in Java, from basic for-loops to Arrays.toString() and streams, with full code examples.
How to Declare and Initialize an Array in Java (2026 Guide + Examples)
Learn how to declare and initialize arrays in Java with clear syntax, memory diagrams, real examples, and best practices. Beginner-friendly, interview-ready. (156 ch