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Extract snippets.json into individual JSON files per category
Each snippet is now stored as category/slug.json alongside its HTML file. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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‎collections/collectors-teeing.json‎

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{
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"id": 26,
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"slug": "collectors-teeing",
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"title": "Collectors.teeing()",
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"category": "collections",
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"difficulty": "intermediate",
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"jdkVersion": "12",
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"oldLabel": "Java 8",
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"modernLabel": "Java 12+",
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"oldApproach": "Two Passes",
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"modernApproach": "teeing()",
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"oldCode": "long count = items.stream().count();\ndouble sum = items.stream()\n .mapToDouble(Item::price)\n .sum();\nvar result = new Stats(count, sum);",
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"modernCode": "var result = items.stream().collect(\n Collectors.teeing(\n Collectors.counting(),\n Collectors.summingDouble(Item::price),\n Stats::new\n )\n);",
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"summary": "Compute two aggregations in a single stream pass.",
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"explanation": "Collectors.teeing() sends each element to two downstream collectors and merges the results. This avoids streaming the data twice or using a mutable accumulator.",
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"whyModernWins": [
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{
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"icon": "⚡",
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"title": "Single pass",
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"desc": "Process the stream once instead of twice."
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},
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{
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"icon": "🧩",
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"title": "Composable",
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"desc": "Combine any two collectors with a merger function."
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},
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{
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"icon": "🔒",
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"title": "Immutable result",
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"desc": "Merge into a record or value object directly."
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}
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],
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"support": "Widely available since JDK 12 (March 2019)"
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}

‎collections/copying-collections-immutably.json‎

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{
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"id": 22,
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"slug": "copying-collections-immutably",
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"title": "Copying collections immutably",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "10",
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"oldLabel": "Java 8",
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"modernLabel": "Java 10+",
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"oldApproach": "Manual Copy + Wrap",
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"modernApproach": "List.copyOf()",
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"oldCode": "List<String> copy =\n Collections.unmodifiableList(\n new ArrayList<>(original)\n );",
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"modernCode": "List<String> copy =\n List.copyOf(original);",
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"summary": "Create an immutable copy of any collection in one call.",
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"explanation": "List.copyOf(), Set.copyOf(), and Map.copyOf() create immutable snapshots of existing collections. If the source is already an immutable collection, no copy is made.",
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"whyModernWins": [
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{
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"icon": "⚡",
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"title": "Smart copy",
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"desc": "Skips the copy if the source is already immutable."
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},
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{
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"icon": "📏",
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"title": "One call",
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"desc": "No manual ArrayList construction + wrapping."
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},
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{
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"icon": "🛡️",
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"title": "Defensive copy",
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"desc": "Changes to the original don't affect the copy."
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}
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],
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"support": "Widely available since JDK 10 (March 2018)"
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}

‎collections/immutable-list-creation.json‎

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{
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"id": 19,
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"slug": "immutable-list-creation",
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"title": "Immutable list creation",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "9",
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"oldLabel": "Java 8",
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"modernLabel": "Java 9+",
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"oldApproach": "Verbose Wrapping",
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"modernApproach": "List.of()",
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"oldCode": "List<String> list =\n Collections.unmodifiableList(\n new ArrayList<>(\n Arrays.asList(\"a\", \"b\", \"c\")\n )\n );",
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"modernCode": "List<String> list =\n List.of(\"a\", \"b\", \"c\");",
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"summary": "Create immutable lists in one clean expression.",
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"explanation": "List.of() creates a truly immutable list — no wrapping, no defensive copy. It's null-hostile (rejects null elements) and structurally immutable. The old way required three nested calls.",
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"whyModernWins": [
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{
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"icon": "📏",
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"title": "One call",
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"desc": "Replace three nested calls with a single factory method."
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},
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{
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"icon": "🔒",
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"title": "Truly immutable",
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"desc": "Not just a wrapper — the list itself is immutable."
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},
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{
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"icon": "🛡️",
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"title": "Null-safe",
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"desc": "Rejects null elements at creation time, failing fast."
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}
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],
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"support": "Widely available since JDK 9 (Sept 2017)"
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}

‎collections/immutable-map-creation.json‎

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{
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"id": 20,
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"slug": "immutable-map-creation",
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"title": "Immutable map creation",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "9",
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"oldLabel": "Java 8",
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"modernLabel": "Java 9+",
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"oldApproach": "Map Builder Pattern",
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"modernApproach": "Map.of()",
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"oldCode": "Map<String, Integer> map = new HashMap<>();\nmap.put(\"a\", 1);\nmap.put(\"b\", 2);\nmap.put(\"c\", 3);\nmap = Collections.unmodifiableMap(map);",
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"modernCode": "Map<String, Integer> map =\n Map.of(\"a\", 1, \"b\", 2, \"c\", 3);",
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"summary": "Create immutable maps inline without a builder.",
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"explanation": "Map.of() accepts key-value pairs inline and returns an immutable map. For more than 10 entries, use Map.ofEntries() with Map.entry() pairs.",
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"whyModernWins": [
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{
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"icon": "📏",
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"title": "Inline creation",
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"desc": "No temporary mutable map needed."
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},
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{
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"icon": "🔒",
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"title": "Immutable result",
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"desc": "The map cannot be modified after creation."
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},
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{
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"icon": "🚫",
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"title": "No null keys/values",
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"desc": "Null entries are rejected immediately."
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}
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],
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"support": "Widely available since JDK 9 (Sept 2017)"
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}

‎collections/immutable-set-creation.json‎

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{
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"id": 21,
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"slug": "immutable-set-creation",
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"title": "Immutable set creation",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "9",
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"oldLabel": "Java 8",
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"modernLabel": "Java 9+",
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"oldApproach": "Verbose Wrapping",
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"modernApproach": "Set.of()",
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"oldCode": "Set<String> set =\n Collections.unmodifiableSet(\n new HashSet<>(\n Arrays.asList(\"a\", \"b\", \"c\")\n )\n );",
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"modernCode": "Set<String> set =\n Set.of(\"a\", \"b\", \"c\");",
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"summary": "Create immutable sets with a single factory call.",
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"explanation": "Set.of() creates a truly immutable set that rejects nulls and duplicate elements at creation time. No more wrapping mutable sets.",
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"whyModernWins": [
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{
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"icon": "📏",
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"title": "Concise",
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"desc": "One line instead of three nested calls."
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},
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{
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"icon": "🚫",
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"title": "Detects duplicates",
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"desc": "Throws if you accidentally pass duplicate elements."
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},
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{
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"icon": "🔒",
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"title": "Immutable",
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"desc": "No add/remove possible after creation."
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}
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],
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"support": "Widely available since JDK 9 (Sept 2017)"
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}

‎collections/map-entry-factory.json‎

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{
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"id": 23,
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"slug": "map-entry-factory",
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"title": "Map.entry() factory",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "9",
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"oldLabel": "Java 8",
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"modernLabel": "Java 9+",
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"oldApproach": "SimpleEntry",
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"modernApproach": "Map.entry()",
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"oldCode": "Map.Entry<String, Integer> e =\n new AbstractMap.SimpleEntry<>(\n \"key\", 42\n );",
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"modernCode": "var e = Map.entry(\"key\", 42);",
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"summary": "Create map entries with a clean factory method.",
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"explanation": "Map.entry() replaces the verbose AbstractMap.SimpleEntry constructor. It returns an immutable entry, making it ideal for Map.ofEntries() and stream operations.",
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"whyModernWins": [
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{
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"icon": "📏",
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"title": "Concise",
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"desc": "One line instead of three with a clearer intent."
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},
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{
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"icon": "🔒",
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"title": "Immutable",
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"desc": "The returned entry cannot be modified."
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},
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{
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"icon": "🧩",
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"title": "Composable",
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"desc": "Works perfectly with Map.ofEntries() for large maps."
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}
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],
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"support": "Widely available since JDK 9 (Sept 2017)"
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}

‎collections/sequenced-collections.json‎

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{
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"id": 24,
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"slug": "sequenced-collections",
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"title": "Sequenced collections",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "21",
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"oldLabel": "Java 8",
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"modernLabel": "Java 21+",
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"oldApproach": "Index Arithmetic",
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"modernApproach": "getFirst/getLast",
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"oldCode": "// Get last element\nvar last = list.get(list.size() - 1);\n// Get first\nvar first = list.get(0);\n// Reverse iteration: manual",
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"modernCode": "var last = list.getLast();\nvar first = list.getFirst();\nvar reversed = list.reversed();",
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"summary": "Access first/last elements and reverse views with clean API methods.",
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"explanation": "SequencedCollection adds getFirst(), getLast(), reversed(), addFirst(), addLast() to List, Deque, SortedSet, and LinkedHashSet. No more size-1 arithmetic or manual reverse iteration.",
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"whyModernWins": [
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{
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"icon": "📖",
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"title": "Self-documenting",
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"desc": "getLast() is clearer than get(size()-1)."
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},
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{
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"icon": "🔄",
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"title": "Reversed view",
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"desc": "reversed() gives a view — no copying needed."
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},
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{
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"icon": "🧩",
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"title": "Uniform API",
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"desc": "Works the same on List, Deque, SortedSet."
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}
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],
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"support": "Widely available since JDK 21 LTS (Sept 2023)"
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}

‎collections/stream-toarray-typed.json‎

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{
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"id": 27,
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"slug": "stream-toarray-typed",
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"title": "Typed stream toArray",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "8",
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"oldLabel": "Pre-Streams",
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"modernLabel": "Java 8+",
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"oldApproach": "Manual Array Copy",
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"modernApproach": "toArray(generator)",
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"oldCode": "List<String> list = getNames();\nString[] arr = new String[list.size()];\nfor (int i = 0; i < list.size(); i++) {\n arr[i] = list.get(i);\n}",
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"modernCode": "String[] arr = getNames().stream()\n .filter(n -> n.length() > 3)\n .toArray(String[]::new);",
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"summary": "Convert streams to typed arrays with a method reference.",
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"explanation": "The toArray(IntFunction) method creates a properly typed array from a stream. The generator (String[]::new) tells the stream what type of array to create.",
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"whyModernWins": [
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{
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"icon": "🎯",
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"title": "Type-safe",
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"desc": "No Object[] cast — the array type is correct."
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},
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{
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"icon": "🔗",
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"title": "Chainable",
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"desc": "Works at the end of any stream pipeline."
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},
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{
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"icon": "📏",
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"title": "Concise",
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"desc": "One expression replaces the manual loop."
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}
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],
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"support": "Widely available since JDK 8 (March 2014)"
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}

‎collections/stream-tolist-shorthand.json‎

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{
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"id": 25,
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"slug": "stream-tolist-shorthand",
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"title": "Stream toList() shorthand",
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"category": "collections",
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"difficulty": "beginner",
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"jdkVersion": "16",
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"oldLabel": "Java 8",
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"modernLabel": "Java 16+",
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"oldApproach": "Collectors.toList()",
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"modernApproach": ".toList()",
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"oldCode": "List<String> names = people.stream()\n .map(Person::name)\n .collect(Collectors.toList());",
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"modernCode": "List<String> names = people.stream()\n .map(Person::name)\n .toList();",
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"summary": "Collect a stream to an unmodifiable list without Collectors.",
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"explanation": "Stream.toList() is a terminal operation that returns an unmodifiable list. It's shorter than .collect(Collectors.toList()) and the result is immutable by default.",
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"whyModernWins": [
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{
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"icon": "📏",
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"title": "Shorter",
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"desc": ".toList() vs .collect(Collectors.toList())."
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},
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{
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"icon": "🔒",
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"title": "Immutable result",
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"desc": "Returns an unmodifiable list by default."
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},
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{
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"icon": "📖",
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"title": "Reads naturally",
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"desc": "stream → map → toList flows like English."
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}
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],
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"support": "Widely available since JDK 16 (March 2021)"
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}

‎collections/unmodifiable-collectors.json‎

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{
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"id": 28,
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"slug": "unmodifiable-collectors",
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"title": "Unmodifiable collectors",
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"category": "collections",
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"difficulty": "intermediate",
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"jdkVersion": "10",
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"oldLabel": "Java 8",
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"modernLabel": "Java 10+",
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"oldApproach": "collectingAndThen",
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"modernApproach": "toUnmodifiable*()",
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"oldCode": "List<String> list = stream.collect(\n Collectors.collectingAndThen(\n Collectors.toList(),\n Collections::unmodifiableList\n )\n);",
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"modernCode": "List<String> list = stream.collect(\n Collectors.toUnmodifiableList()\n);",
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"summary": "Collect directly to unmodifiable collections.",
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"explanation": "Java 10 added toUnmodifiableList(), toUnmodifiableSet(), and toUnmodifiableMap() collectors. No more wrapping with collectingAndThen.",
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"whyModernWins": [
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{
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"icon": "📏",
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"title": "Direct",
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"desc": "One collector instead of wrapping with collectingAndThen."
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},
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{
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"icon": "🔒",
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"title": "Immutable",
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"desc": "Result cannot be modified — no accidental mutations."
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},
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{
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"icon": "🚫",
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"title": "Null-safe",
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"desc": "Rejects null elements during collection."
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}
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],
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"support": "Widely available since JDK 10 (March 2018)"
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}

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