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Add Java 21 direct execution instructions for README examples
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‎README.md‎

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@@ -15,6 +15,18 @@ We welcome contributions to the JTD Validator incubating within this repo.
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## Usage Examples
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### Running the Examples
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To try the examples from this README, build the project and run the standalone example class:
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```bash
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mvn package
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java -cp ./json-java21/target/java.util.json-*.jar:./json-java21/target/test-classes \
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jdk.sandbox.java.util.json.examples.ReadmeExamples
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```
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*Replace `*` with the actual version number from the JAR filename.*
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## API Overview
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The API provides immutable JSON value types:

‎json-java21/src/test/java/jdk/sandbox/java/util/json/examples/ReadmeExamples.java‎

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package jdk.sandbox.java.util.json.examples;
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import jdk.sandbox.java.util.json.*;
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import java.util.List;
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import java.util.Map;
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/**
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* Standalone examples demonstrating the java.util.json API.
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* This file contains runnable examples that match the README documentation.
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*
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* To run:
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* mvn compile exec:java -Dexec.mainClass="jdk.sandbox.java.util.json.examples.ReadmeExamples"
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*/
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public class ReadmeExamples {
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// Domain model using records
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record User(String name, String email, boolean active) {}
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record Team(String teamName, List<User> members) {}
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public static void main(String[] args) {
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System.out.println("=== Java.util.json API Examples ===\n");
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quickStartExample();
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recordMappingExample();
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builderPatternExample();
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streamingProcessingExample();
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errorHandlingExample();
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displayFormattingExample();
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System.out.println("\n=== All examples completed successfully! ===");
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}
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static void quickStartExample() {
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System.out.println("1. Quick Start Example");
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System.out.println("----------------------");
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// Basic parsing example
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String jsonString = "{\"name\":\"Alice\",\"age\":30}";
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JsonValue value = Json.parse(jsonString);
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System.out.println("Parsed JSON: " + jsonString);
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System.out.println("Value type: " + value.getClass().getSimpleName());
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JsonObject obj = (JsonObject) value;
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String name = ((JsonString) obj.members().get("name")).string();
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long age = ((JsonNumber) obj.members().get("age")).toLong();
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System.out.println("Extracted name: " + name);
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System.out.println("Extracted age: " + age);
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System.out.println("Round trip: " + value.toString());
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System.out.println();
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}
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static void recordMappingExample() {
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System.out.println("2. Record Mapping Example");
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System.out.println("-------------------------");
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// Create a team with users
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Team team = new Team("Engineering", List.of(
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new User("Alice", "alice@example.com", true),
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new User("Bob", "bob@example.com", false)
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));
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System.out.println("Original team: " + team);
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// Convert records to JSON using typed factories
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JsonValue teamJson = JsonObject.of(Map.of(
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"teamName", JsonString.of(team.teamName()),
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"members", JsonArray.of(team.members().stream()
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.map(u -> JsonObject.of(Map.of(
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"name", JsonString.of(u.name()),
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"email", JsonString.of(u.email()),
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"active", JsonBoolean.of(u.active())
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)))
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.toList())
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));
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System.out.println("JSON representation:");
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System.out.println(teamJson.toString());
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// Parse JSON back to records
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JsonObject parsed = (JsonObject) Json.parse(teamJson.toString());
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Team reconstructed = new Team(
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((JsonString) parsed.members().get("teamName")).string(),
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((JsonArray) parsed.members().get("members")).elements().stream()
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.map(v -> {
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JsonObject member = (JsonObject) v;
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return new User(
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((JsonString) member.members().get("name")).string(),
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((JsonString) member.members().get("email")).string(),
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((JsonBoolean) member.members().get("active")).bool()
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);
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})
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.toList()
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);
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System.out.println("Reconstructed team: " + reconstructed);
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System.out.println("Round trip successful: " + team.equals(reconstructed));
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System.out.println();
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}
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static void builderPatternExample() {
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System.out.println("3. Builder Pattern Example");
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System.out.println("-------------------------");
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// Building a REST API response
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JsonObject response = JsonObject.of(Map.of(
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"status", JsonString.of("success"),
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"data", JsonObject.of(Map.of(
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"user", JsonObject.of(Map.of(
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"id", JsonNumber.of(12345),
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"name", JsonString.of("John Doe"),
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"roles", JsonArray.of(List.of(
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JsonString.of("admin"),
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JsonString.of("user")
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))
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)),
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"timestamp", JsonNumber.of(System.currentTimeMillis())
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)),
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"errors", JsonArray.of(List.of())
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));
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System.out.println("API Response:");
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System.out.println(Json.toDisplayString(response, 2));
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System.out.println();
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}
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static void streamingProcessingExample() {
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System.out.println("4. Streaming Processing Example");
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System.out.println("--------------------------------");
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// Create a large array of user records
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String largeJsonArray = """
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[
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{"name": "Alice", "email": "alice@example.com", "active": true},
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{"name": "Bob", "email": "bob@example.com", "active": false},
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{"name": "Charlie", "email": "charlie@example.com", "active": true},
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{"name": "David", "email": "david@example.com", "active": false},
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{"name": "Eve", "email": "eve@example.com", "active": true}
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]
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""";
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// Process a large array of records
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JsonArray items = (JsonArray) Json.parse(largeJsonArray);
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List<String> activeUserEmails = items.elements().stream()
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.map(v -> (JsonObject) v)
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.filter(obj -> ((JsonBoolean) obj.members().get("active")).bool())
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.map(obj -> ((JsonString) obj.members().get("email")).string())
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.toList();
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System.out.println("Active user emails: " + activeUserEmails);
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System.out.println();
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}
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static void errorHandlingExample() {
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System.out.println("5. Error Handling Example");
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System.out.println("------------------------");
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// Valid JSON parsing
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String validJson = "{\"valid\": true}";
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try {
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JsonValue value = Json.parse(validJson);
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System.out.println("Valid JSON parsed successfully: " + value);
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} catch (JsonParseException e) {
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System.out.println("Unexpected error: " + e.getMessage());
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}
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// Invalid JSON parsing
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String invalidJson = "{invalid json}";
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try {
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JsonValue value = Json.parse(invalidJson);
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System.out.println("This shouldn't print");
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} catch (JsonParseException e) {
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System.out.println("Caught expected error: " + e.getMessage());
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System.out.println("Error at line " + e.getErrorLine() + ", position " + e.getErrorPosition());
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}
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System.out.println();
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}
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static void displayFormattingExample() {
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System.out.println("6. Display Formatting Example");
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System.out.println("-----------------------------");
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// Create a structured JSON
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JsonObject data = JsonObject.of(Map.of(
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"name", JsonString.of("Alice"),
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"scores", JsonArray.of(List.of(
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JsonNumber.of(85),
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JsonNumber.of(90),
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JsonNumber.of(95)
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))
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));
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// Format for display
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String formatted = Json.toDisplayString(data, 2);
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System.out.println("Formatted JSON:");
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System.out.println(formatted);
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System.out.println();
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}
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}

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