Exploring Collectors
summary
Walks through concrete Java Stream code showing where Collectors replace error-prone reduce/for-each patterns, demonstrates Collectors utility class methods (toList/toSet/toUnmodifiableList, joining, groupingBy, partitioningBy, mapping, counting, collectingAndThen, maxBy/minBy, teeing, flatMap) and live-codes conversions (map→collect, map+flatMap, grouping to buckets, counting yields Long→int via collectingAndThen). Reproduces a race bug from shared mutation and proves collectors work with parallel streams, argues to avoid shared mutability and prefer immutable collectors for correct, concurrent results.
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chapters (22)
- 0:00Introduction
- 1:18Why Java
- 2:37Create People
- 8:23Reduce
- 14:04Lazy Evaluation
- 15:00Immutability
- 16:32Programming languages
- 17:39Example
- 23:58Reduce Function
- 25:12Combine Collections
- 29:37Collectors
- 33:34Using Collectors
- 35:27Creating a Map
- 38:10Create a Map
- 40:01Get a List of Ages
- 41:08Unmodifiable Lists
- 42:31commaseparated lists
- 45:30collecting
- 47:07filters
- 50:20partitioning
- 52:04by name
- 54:07add
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