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Stream API
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Stream API

Stream API

1. Fundamentals and Functional Capabilities of Stream API
ArchitecturePrinciplesWhat Is a Functional Interface?Predicate: Data FilteringChallenge: Filtering Corporate Email AddressesFunction: Data TransformationChallenge: Income Tax CalculationComparable: Natural Ordering of DataComparator: Custom Comparison of DataChallenge: Sorting Employees Consumer: Processing Data Supplier: Data GenerationBi-versions of Functional InterfacesChallenge: Filtering Users by Two CriteriaBinaryOperator: Combining Two Values
2. Intermediate Operations in Stream API
Transforming Elements with the map() MethodFiltering Elements with the filter() MethodChallenge: Factory Product FilteringWorking with Nested Structures with the flatMap() MethodArranging Items in Order with the sorted() MethodChallenge: Selecting the Best Cars on the Production LineEliminating Duplicates with the distinct() MethodChallenge: Factory Quality ControlRestricting and Skipping Elements with the limit() and skip() MethodsChallenge: Finding the Top 3 Hardest-Working EmployeesIntermediate Processing with the peek() Method
3. Terminal Operations in the Stream API
collect() Gathering Stream Elements into a CollectionChallenge: Build a Custom Collector for Category CountingCollectors Utility Class for Stream APIProcessing Elements with the forEach() MethodHandling Values with the Optional ClassAggregating Elements with the reduce() MethodChallenge: Calculating Total Cost with Discounts and TaxCalculating Stream Statistics with count(), max(), and min()Retrieving Stream Summary Metrics with summaryStatistics() MethodRetrieving Elements from a Stream with findFirst() and findAny()Challenge: Selecting Random Products Within a CategoryChecking Stream Elements Against a Condition with allMatch()Challenge: Ensuring Fast Delivery for Expensive Products
4. Practical Applications of Stream API
Real-World Examples of Using Stream APIPerformance in Stream APIException Handling in Stream APISummary

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Challenge: Build a Custom Collector for Category Counting

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You need to implement a custom Collector that processes a list of products and counts how many products belong to each category.

  1. In the supplier() method, return a new HashMap.
  2. In the accumulator() method, call the get() method on the product map to retrieve the value of the "category" key and pass it as the first parameter of the merge() method.
  3. For the second parameter in the same method, provide the initial value (1).
  4. In the combiner() method, pass the key of map2 as the first parameter of the merge() method.
  5. For the second parameter in the same method, pass the value of the map2.
  6. In the finisher() method, return the map without modifying it using a lambda.
  7. In the characteristics() method, return a set that ensures the collection remains unchanged (IDENTITY_FINISH).
  8. In the collect() method, pass the implementation of the Collector interface (CategoryCountCollector).

Lösning

java

solution

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Avsnitt 3. Kapitel 2
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book
Challenge: Build a Custom Collector for Category Counting

Uppgift

Swipe to start coding

You need to implement a custom Collector that processes a list of products and counts how many products belong to each category.

  1. In the supplier() method, return a new HashMap.
  2. In the accumulator() method, call the get() method on the product map to retrieve the value of the "category" key and pass it as the first parameter of the merge() method.
  3. For the second parameter in the same method, provide the initial value (1).
  4. In the combiner() method, pass the key of map2 as the first parameter of the merge() method.
  5. For the second parameter in the same method, pass the value of the map2.
  6. In the finisher() method, return the map without modifying it using a lambda.
  7. In the characteristics() method, return a set that ensures the collection remains unchanged (IDENTITY_FINISH).
  8. In the collect() method, pass the implementation of the Collector interface (CategoryCountCollector).

Lösning

java

solution

Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 2
Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Vi beklagar att något gick fel. Vad hände?
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