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Courses / Modern Java

Java Collectors

intermediate8 lessons

The Supplier/Accumulator/Combiner/Finisher model, every built-in Collector with its gotchas, groupingBy with downstream collectors, partitioningBy, toMap key collisions, building a custom Collector from scratch, and Collector characteristics (CONCURRENT, UNORDERED, IDENTITY_FINISH).

// Lessons

  1. 01

    What Is a Collector? — Supplier, Accumulator, Combiner, Finisher

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  2. 02

    toList, toSet, toUnmodifiableList, toMap — The Basics and Gotchas

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  3. 03

    groupingBy — Partitioning a Stream by a Classifier

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  4. 04

    partitioningBy — Splitting into Two Groups

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  5. 05

    Downstream Collectors — counting, summingInt, mapping, joining

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  6. 06

    Collectors.toMap — Key Collisions and the Merge Function

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  7. 07

    Custom Collector Implementation — Building One from Scratch

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  8. 08

    Collector Characteristics — CONCURRENT, UNORDERED, IDENTITY_FINISH

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