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Types & classes99 in github.com/ZahidFKhan/Streams-API-Practices

⨍ Functions 256◇ Types & classes 99

ClassA_CountEvenNumbers

Count even numbers: Example: Input = [1,2,3,4,5,6] Output = 3 Explanation: (2, 4, 6) are even numbers.

src/test/java/com/github/streams/practice/a_easy_problems/numbers/A_CountEvenNumbers.java:16

ClassA_GenerateAPrimeNumberStream

src/test/java/com/github/streams/practice/c_hard_problems/numbers/A_GenerateAPrimeNumberStream.java:8

ClassA_Lambdas

This set of exercises is about lambdas and method references. You will write a lambda or method reference corresponding to each of several different f

src/test/java/com/github/streams/practice/functional_interfaces/solutions/A_Lambdas.java:19

ClassA_MatchesNoOfVowelsTest

Finds the words with the given number of vowels in a given string. Example: <pre> "The quick brown fox jumps right over the little lazy do

src/test/java/com/github/streams/practice/a_easy_problems/strings/A_MatchesNoOfVowelsTest.java:34

ClassA_MatchesNoOfVowelsTest

Finds the words with the given number of vowels in a given string. Example: <pre> "The quick brown fox jumps right over the little lazy do

src/test/java/com/github/streams/practice/b_medium_problems/strings/A_MatchesNoOfVowelsTest.java:34

ClassA_MinSalaryInEachDept

src/test/java/com/github/streams/practice/b_medium_problems/employee/A_MinSalaryInEachDept.java:25

ClassA_PredicateTest

src/test/java/com/github/streams/practice/functional_interfaces/A_PredicateTest.java:8

ClassA_SumOfNumbers

src/test/java/com/github/streams/practice/b_medium_problems/numbers/A_SumOfNumbers.java:16

ClassB_Comparators

Exercises to create comparators using lambda expressions and using the Comparator combinators. Some of the exercises use a Person class, which is a si

src/test/java/com/github/streams/practice/functional_interfaces/solutions/B_Comparators.java:15

ClassB_FunctionTest

src/test/java/com/github/streams/practice/functional_interfaces/B_FunctionTest.java:9

ClassB_LargestWordTest

src/test/java/com/github/streams/practice/a_easy_problems/strings/B_LargestWordTest.java:7

ClassB_LargestWordTest

src/test/java/com/github/streams/practice/b_medium_problems/strings/B_LargestWordTest.java:7

ClassB_LengthOfLargestConsecutiveSequence

src/test/java/com/github/streams/practice/c_hard_problems/numbers/B_LengthOfLargestConsecutiveSequence.java:35

ClassB_MapCelsiusToFahrenheit

Exercise focusing on the Stream.map() function. The goal is to convert a list of temperatures from Celsius (Integers) to Fahrenheit (Doubles) using th

src/test/java/com/github/streams/practice/a_easy_problems/numbers/B_MapCelsiusToFahrenheit.java:18

ClassB_MaxSalaryInEachDept

src/test/java/com/github/streams/practice/b_medium_problems/employee/B_MaxSalaryInEachDept.java:25

ClassB_SumOfUniqueNumbers

Calculates the sum of unique elements in an array. Example: Input: [5, 6, 7, 8, 5, 5, 8, 8, 7] Output: 26

src/test/java/com/github/streams/practice/b_medium_problems/numbers/B_SumOfUniqueNumbers.java:16

ClassC_ConsumerTest

src/test/java/com/github/streams/practice/functional_interfaces/C_ConsumerTest.java:12

ClassC_DefaultMethodsTest

This set of exercises covers new default methods on the Collections and related APIs.

src/test/java/com/github/streams/practice/functional_interfaces/solutions/C_DefaultMethodsTest.java:16

ClassC_LengthOfCityTest

Calculates the length of city names that start with 'm' or 'M' and returns a map of city name to its length. Example: Input: ["Mumbai", "Munn

src/test/java/com/github/streams/practice/a_easy_problems/strings/C_LengthOfCityTest.java:19

ClassC_LengthOfCityTest

Calculates the length of city names that start with 'm' or 'M'. <h3>Example Cities</h3> <ul> <li>Mumbai <li>Munnar <li>Chennai <li

src/test/java/com/github/streams/practice/b_medium_problems/strings/C_LengthOfCityTest.java:23

ClassC_SumOfDigits

Calculates the sum of digits of a given integer. This method takes an integer as input, breaks it down into individual digits, and returns their s

src/test/java/com/github/streams/practice/b_medium_problems/numbers/C_SumOfDigits.java:19

ClassC_SumOfSalaryInEachDept

src/test/java/com/github/streams/practice/b_medium_problems/employee/C_SumOfSalaryInEachDept.java:26

ClassC_UniqueEmailAddresses

Imagine you’re building a registration system for a website. Sometimes, due to user error or system retries, duplicate emails get stored in your list.

src/test/java/com/github/streams/practice/a_easy_problems/numbers/C_UniqueEmailAddresses.java:18

ClassD_NumberOfEmployeeInEachDept

src/test/java/com/github/streams/practice/b_medium_problems/employee/D_NumberOfEmployeeInEachDept.java:28

ClassD_NumberOfOccurencesOfEachCharacterTest

Count the number of occurrences of each character in a string (spaces excluded). Example: Input: "the quick brown fox jumps right over the li

src/test/java/com/github/streams/practice/a_easy_problems/strings/D_NumberOfOccurencesOfEachCharacterTest.java:17

ClassD_NumberOfOccurencesOfEachCharacterTest

src/test/java/com/github/streams/practice/b_medium_problems/strings/D_NumberOfOccurencesOfEachCharacterTest.java:9

ClassD_SimpleStreams

This set of exercises covers simple stream pipelines, including intermediate operations and basic collectors. Some of these exercises use a Buffer

src/test/java/com/github/streams/practice/functional_interfaces/solutions/D_SimpleStreams.java:21

ClassD_SupplierTest

src/test/java/com/github/streams/practice/functional_interfaces/D_SupplierTest.java:9

ClassD_ValidNumbersOnly

Extracts integers from a list of strings. Example: Input: ["as", "123", "32", "2as"] Output: [123, 32] Explanation: Parses strin

src/test/java/com/github/streams/practice/a_easy_problems/numbers/D_ValidNumbersOnly.java:16

ClassD_ValidNumbersOnly

Extracts integers from a list of strings. Example: Input: ["as", "123", "32", "2as"] Output: [123, 32] Explanation: Parses strin

src/test/java/com/github/streams/practice/b_medium_problems/numbers/D_ValidNumbersOnly.java:16

EnumDepartment

src/test/java/com/github/streams/practice/b_medium_problems/employee/ignore/domain_related/Department.java:3

InterfaceDoubleToIntBiFunction

src/test/java/com/github/streams/practice/functional_interfaces/F_ComparatorTest.java:231

InterfaceDoubleToIntBiFunction

src/test/java/com/github/streams/practice/functional_interfaces/solutions/B_Comparators.java:260

ClassDummyData

src/test/java/com/github/streams/practice/a_easy_problems/numbers/data/DummyData.java:9

ClassDummyData

src/test/java/com/github/streams/practice/b_medium_problems/numbers/data/DummyData.java:9

ClassDummyEmployees

src/test/java/com/github/streams/practice/b_medium_problems/employee/ignore/domain_related/dummy_data/DummyEmployees.java:16

ClassDummyProjects

src/test/java/com/github/streams/practice/b_medium_problems/employee/ignore/domain_related/dummy_data/DummyProjects.java:8

ClassE_BiFunctionTest

src/test/java/com/github/streams/practice/functional_interfaces/E_BiFunctionTest.java:9

ClassE_EmployeesBelongToEachDept

src/test/java/com/github/streams/practice/b_medium_problems/employee/E_EmployeesBelongToEachDept.java:35

ClassE_IntermediateStreams

This set of exercises covers more advanced stream operations longer stream pipelines, and simple reductions.

src/test/java/com/github/streams/practice/functional_interfaces/solutions/E_IntermediateStreams.java:27

ClassE_NumberOfOccurencesOfEachWordTest

Count the number of occurrences of each word in a string. Example: Input: "the quick brown fox jumps right over the little lazy dog little" <

src/test/java/com/github/streams/practice/a_easy_problems/strings/E_NumberOfOccurencesOfEachWordTest.java:17

ClassE_NumberOfOccurencesOfEachWordTest

src/test/java/com/github/streams/practice/b_medium_problems/strings/E_NumberOfOccurencesOfEachWordTest.java:9

ClassE_RemoveDuplicates

Removes duplicates from a list of integers. Input: [1, 2, 2, 3, 4, 4, 5] Output: [1, 2, 3, 4, 5] Explanation: R

src/test/java/com/github/streams/practice/a_easy_problems/numbers/E_RemoveDuplicates.java:17

ClassEasyNumbersProblemSolution

src/test/java/com/github/streams/practice/a_easy_problems/numbers/EasyNumbersProblemSolution.java:7

ClassEmployee

src/test/java/com/github/streams/practice/b_medium_problems/employee/ignore/domain_related/Employee.java:5

ClassF_AdvancedStreams

This set of exercises covers advanced stream operations, including grouping collectors, composition of collectors, and customized collectors.

src/test/java/com/github/streams/practice/functional_interfaces/solutions/F_AdvancedStreams.java:27

ClassF_AscendingNumberValue

Re-arranges the elements of a numeric array to form the smallest possible value. Example: Input: [1, 34, 3, 98, 9, 76, 45, 4] Output: 1334445

src/test/java/com/github/streams/practice/a_easy_problems/numbers/F_AscendingNumberValue.java:17

ClassF_AscendingNumberValue

Re-arranges the elements of a numeric array to form the smallest possible value. Example: Input: [1, 34, 3, 98, 9, 76, 45, 4] Output: 1334445

src/test/java/com/github/streams/practice/b_medium_problems/numbers/F_AscendingNumberValue.java:17

ClassF_ComparatorTest

src/test/java/com/github/streams/practice/functional_interfaces/F_ComparatorTest.java:11

ClassF_ConcatenationOfStrings

Given a list of strings, concatenate all strings separated by a comma using Java Streams. Example: Input: ["Hellow", "World", "Hello", "World

src/test/java/com/github/streams/practice/a_easy_problems/strings/F_ConcatenationOfStrings.java:15

ClassF_ConcatenationOfStrings

src/test/java/com/github/streams/practice/b_medium_problems/strings/F_ConcatenationOfStrings.java:8

ClassF_ManagerWithMaxEmployees

src/test/java/com/github/streams/practice/b_medium_problems/employee/F_ManagerWithMaxEmployees.java:9

ClassG_DescendingNumberValue

Re-arranges the elements of a numeric array to form the highest possible value. Example: Input: [1, 34, 3, 98, 9, 76, 45, 4] Output: "99

src/test/java/com/github/streams/practice/a_easy_problems/numbers/G_DescendingNumberValue.java:16

ClassG_DescendingNumberValue

src/test/java/com/github/streams/practice/b_medium_problems/numbers/G_DescendingNumberValue.java:14

ClassG_EmployeesWhoWorkedOnMostProject

src/test/java/com/github/streams/practice/b_medium_problems/employee/G_EmployeesWhoWorkedOnMostProject.java:48

ClassG_RemoveDuplicateCharactersTest

Remove duplicate characters from a string, preserving the order of first occurrence. Example: Input: "dabfcadef" Output: "dabfce" E

src/test/java/com/github/streams/practice/a_easy_problems/strings/G_RemoveDuplicateCharactersTest.java:16

ClassG_RemoveDuplicateCharactersTest

src/test/java/com/github/streams/practice/b_medium_problems/strings/G_RemoveDuplicateCharactersTest.java:8

ClassG_RunnableTest

src/test/java/com/github/streams/practice/functional_interfaces/G_RunnableTest.java:8

ClassH_ReverseANumber

Reverse the digits of an integer. Example: Input: 12345 Output: 54321

src/test/java/com/github/streams/practice/a_easy_problems/numbers/H_ReverseANumber.java:15

ClassH_ReverseANumber

Reverses the digits of a given integer. Example: Input: 1234 Output: 4321

src/test/java/com/github/streams/practice/b_medium_problems/numbers/H_ReverseANumber.java:15

ClassH_ReverseStringWithSpecialCharactersTest

Reverse a string that may contain special characters and Unicode (e.g., emojis). Example: Input: "Hello world! This is a test. 😅" Output

src/test/java/com/github/streams/practice/a_easy_problems/strings/H_ReverseStringWithSpecialCharactersTest.java:14

ClassH_ReverseStringWithSpecialCharactersTest

Unit test for reversing a string that contains special characters. This test class is designed to verify the correctness of a method that reverses

src/test/java/com/github/streams/practice/b_medium_problems/strings/H_ReverseStringWithSpecialCharactersTest.java:15

ClassHardNumbersProblemSolution

src/test/java/com/github/streams/practice/c_hard_problems/numbers/HardNumbersProblemSolution.java:11

ClassI_SecondHighestWordTest

Find the second-largest word (by character length) in a given string. Example: Input: "I am interested123455 to grow in my organization"

src/test/java/com/github/streams/practice/a_easy_problems/strings/I_SecondHighestWordTest.java:16

ClassI_SecondHighestWordTest

src/test/java/com/github/streams/practice/b_medium_problems/strings/I_SecondHighestWordTest.java:8

ClassI_SegregateEvenOddNumbers

Divides a list of integers into two separate lists, one containing all even numbers and the other containing all odd numbers. Input: {1, 2, 3, 4, 5, 6

src/test/java/com/github/streams/practice/b_medium_problems/numbers/I_SegregateEvenOddNumbers.java:14

ClassIdentity

src/test/java/com/github/streams/practice/b_medium_problems/employee/ignore/domain_related/Identity.java:3

ClassJ_MeanOfNumbers

Calculate the mean (average) of a list of integers. Example: Input: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] <

src/test/java/com/github/streams/practice/a_easy_problems/numbers/J_MeanOfNumbers.java:15

ClassJ_MeanOfNumbers

Calculates the arithmetic mean (average) of a list of integers. Example: Input: [1, 2, 3, 4, 5, ..., 20] Output: 10.5

src/test/java/com/github/streams/practice/b_medium_problems/numbers/J_MeanOfNumbers.java:15

ClassJ_SortListBasedOn2ndCharacterTest

Sort a list of strings alphabetically by their second character. Example: Input: ["banana", "apple", "cherry", "date"] Output: ["date",

src/test/java/com/github/streams/practice/a_easy_problems/strings/J_SortListBasedOn2ndCharacterTest.java:18

ClassJ_SortListBasedOn2ndCharacterTest

src/test/java/com/github/streams/practice/b_medium_problems/strings/J_SortListBasedOn2ndCharacterTest.java:10

ClassK_FindDuplicateStrings

Find all strings that appear more than once in a list. Example: Input: ["Hellow", "World", "How", "are", "you", "How", "are", "you"] Out

src/test/java/com/github/streams/practice/a_easy_problems/strings/K_FindDuplicateStrings.java:16

ClassK_FindDuplicateStrings

src/test/java/com/github/streams/practice/b_medium_problems/strings/K_FindDuplicateStrings.java:8

ClassK_IntArray2DToListConverter

Convert a 2D integer array into a List of Lists of Integers using streams. Example: Input: {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}} Output: [[1

src/test/java/com/github/streams/practice/a_easy_problems/numbers/K_IntArray2DToListConverter.java:16

ClassK_IntArray2DToListConverter

Converts a 2D primitive int array into a {@code List<List<Integer>>}. Example: Input: {{1, 2}, {3, 4}, {5, 6}} Output: [[1, 2], [3, 4], [5

src/test/java/com/github/streams/practice/b_medium_problems/numbers/K_IntArray2DToListConverter.java:16

ClassL_ConvertListOfCharactersToString

Convert a list of Character objects into a single concatenated String. Example: Input: ['A', 'B', 'C', 'D', ..., 'Z'] Output: "ABCDEFGHI

src/test/java/com/github/streams/practice/a_easy_problems/strings/L_ConvertListOfCharactersToString.java:15

ClassL_ConvertListOfCharactersToString

src/test/java/com/github/streams/practice/b_medium_problems/strings/L_ConvertListOfCharactersToString.java:8

ClassL_GenerateInfinitePrimeNumberStream

Generates a list of the first N prime numbers using an infinite stream. Example: Input: N = 5 Output: [2, 3, 5, 7, 11]

src/test/java/com/github/streams/practice/b_medium_problems/numbers/L_GenerateInfinitePrimeNumberStream.java:15

ClassM_UpperCaseOddLengthWords

Given a list of words, filter out only the words with an odd character length and convert them to uppercase. Example: Input: ["alfa", "bravo"

src/test/java/com/github/streams/practice/a_easy_problems/strings/M_UpperCaseOddLengthWords.java:17

ClassM_UpperCaseOddLengthWords

src/test/java/com/github/streams/practice/b_medium_problems/strings/M_UpperCaseOddLengthWords.java:8

ClassMediumNumbersProblemSolution

src/test/java/com/github/streams/practice/b_medium_problems/numbers/MediumNumbersProblemSolution.java:10

ClassMediumStringProblemsSolution

Reference solutions for medium-tier string problems. The 12 methods below are identical to {@link com.github.streams.practice.a_easy_problems.stri

src/test/java/com/github/streams/practice/b_medium_problems/strings/MediumStringProblemsSolution.java:18

ClassN_FirstNonRepeatingCharacterTest

Find the first character in a string that does not repeat anywhere else in the string. (Classic Google interview question) Example: Input: "T

src/test/java/com/github/streams/practice/a_easy_problems/strings/N_FirstNonRepeatingCharacterTest.java:17

ClassN_FirstNonRepeatingCharacterTest

Given a String find the first non-repeating character: String = The quick brown fox jumps over the lazy dog, find the first non-repeated character

src/test/java/com/github/streams/practice/b_medium_problems/strings/N_FirstNonRepeatingCharacterTest.java:14

ClassN_GroupingOfNumbersTest

src/test/java/com/github/streams/practice/a_easy_problems/numbers/N_GroupingOfNumbersTest.java:31

ClassN_GroupingOfNumbersTest

src/test/java/com/github/streams/practice/b_medium_problems/numbers/N_GroupingOfNumbersTest.java:31

ClassO_UniqueEmailCount

Given a list of employees, each with an email address, extract all unique email domains and count how many employees use each domain. Example: <br

src/test/java/com/github/streams/practice/a_easy_problems/strings/O_UniqueEmailCount.java:21

ClassO_UniqueEmailCount

src/test/java/com/github/streams/practice/b_medium_problems/strings/O_UniqueEmailCount.java:17

ClassP_WordWithMaxNumberOfVowelsTest

Given a string, find the highest number of vowels present in any single word. Example: Input: "HELLO HOW ARE YOU" Output: 2 Explana

src/test/java/com/github/streams/practice/a_easy_problems/strings/P_WordWithMaxNumberOfVowelsTest.java:17

ClassP_WordWithMaxNumberOfVowelsTest

Given A String Find the highest number of vowels present in a word. Example: INPUT: HELLO HOW ARE YOU OUTPUT: 2 EXPLANATION: HELLO contains 2 vowe

src/test/java/com/github/streams/practice/b_medium_problems/strings/P_WordWithMaxNumberOfVowelsTest.java:14

ClassPerson

src/test/java/com/github/streams/practice/functional_interfaces/F_ComparatorTest.java:13

ClassPerson

src/test/java/com/github/streams/practice/functional_interfaces/solutions/B_Comparators.java:17

ClassProblemSolutions

src/test/java/com/github/streams/practice/b_medium_problems/ProblemSolutions.java:10

ClassProject

src/test/java/com/github/streams/practice/b_medium_problems/employee/ignore/domain_related/Project.java:3

ClassQ_FrequentVowelPlusConstant

src/test/java/com/github/streams/practice/b_medium_problems/strings/Q_FrequentVowelPlusConstant.java:58

ClassScanTest

src/test/java/com/github/streams/practice/gatherers/ScanTest.java:12

ClassStringProblemsSolution

src/test/java/com/github/streams/practice/a_easy_problems/strings/StringProblemsSolution.java:7

ClassTotalAndDistinct

Count the total number of words and the number of distinct, lower case words in a stream, in one pass. This exercise uses a helper class that defines

src/test/java/com/github/streams/practice/functional_interfaces/solutions/F_AdvancedStreams.java:343

ClassWindowFixedTest

src/test/java/com/github/streams/practice/gatherers/WindowFixedTest.java:17