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feature: integrate devin/1786033698-presentation-modernization
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‎README.md‎

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# springboot-java8
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The project is made on spring boot. The project summarize the new features present in Java 8.
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It contain list of harcoded topics list. You can call the apis's with POSTMAN to add,delete,update Topic list
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In addition, it uses
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1) Java 8 NIO methods
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2) String operations
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3) Stream operations
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4) IntStream functions
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5) Functional interface
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6) Lambda functions
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7) Optional datatype
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8) Foreach loops
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9) Default and Static methods in interface
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10) Java 8 LocalDateTime API
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11) Pattern
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## Getting Started
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1) Download or clone the project with link
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(https://github.com/RehmanMuradAli/springboot-java8/)
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## Available API's
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Greetings
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```
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GET /
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```
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Get all Topics in List
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```
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GET /topic
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```
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Get Topic of given ID
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```
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GET /topic/{id}
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```
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Add Topic in List
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```
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POST /topic
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```
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Update Topic of given ID
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```
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PUT /topic/{id}
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```
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Delete Topic of given ID
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```
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DELETE /topic/{id}
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```
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A small Spring Boot REST service whose purpose is to **demonstrate Java language features** — originally the Java 8
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feature set, which is still what the code shows off. The name stuck, but the project itself now builds and runs on
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**Java 21 with Spring Boot 3.5.16**.
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Get all Topics whose ID's length is greater than minLength
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```
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GET /topic/minimum/length/{minLength}
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```
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The domain is deliberately trivial: an in-memory, hardcoded list of `Topic` objects that you can create, read, update
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and delete over HTTP, plus a few endpoints that exist purely to print the result of stream / string / file operations.
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Get all Topics sorted by ID
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```
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GET /topic/sort
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```
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## Java 8 features demonstrated
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String Operations on Topic List
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```
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GET /topic/string/operation
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```
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1. NIO.2 file APIs (`Files.list`, `Files.find`, `Files.walk`, `Files.newBufferedReader`)
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2. String operations (`String.join`, `String.chars`)
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3. Stream operations (`filter`, `map`, `sorted`, `Collectors.joining`)
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4. `IntStream` (`IntStream.range` for index lookups)
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5. Functional interfaces (`CustomPredicate<T>`)
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6. Lambda expressions
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7. `Optional` / `OptionalInt`
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8. `forEach` loops
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9. `default` and `static` methods on interfaces (`TimeClient`)
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10. The `java.time` API (`LocalDateTime`, `ZonedDateTime`, `ChronoUnit`)
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11. `Pattern` as a stream source and as a predicate (`splitAsStream`, `asPredicate`)
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12. try-with-resources over streams of paths
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File Operations on Topic List
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```
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GET /topic/file/operation
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```
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Java 8 Date Time example
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## Java 21 idioms in use
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The application was migrated from Spring Boot 2.0.2 / Java 8 to Spring Boot 3.5.16 / Java 21, and the presentation
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layer has been rewritten to use the modern language features that replace what the old code did by hand:
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- **Text blocks** (Java 15) for the multi-part responses of `/datetime`, `/topic/string/operation` and
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`/topic/file/operation`, using `\` line-continuation escapes so the responses stay on a single line.
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- **`String.formatted(...)`** (Java 15) instead of `String.format(...)` and `+` concatenation.
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- Label templates are `private static final` constants rather than mutable instance fields.
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## Requirements
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- JDK 21 (the build sets `<java.version>21</java.version>`)
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- Maven is **not** required — use the bundled Maven Wrapper (`./mvnw`, Maven 3.9.9)
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- `curl`, HTTPie or Postman to call the API
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## Getting started
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```bash
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git clone https://github.com/COG-GTM/springboot-java8.git
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cd springboot-java8
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# compile, run the test suite and package the jar
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./mvnw clean verify
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# run the application (listens on http://localhost:8080)
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./mvnw spring-boot:run
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```
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GET /datetime
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You can also run the packaged jar directly:
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```bash
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java -jar target/gs-spring-boot-0.1.0.jar
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```
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> The Gradle build has been removed; Maven is the only supported build.
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Every push and pull request is built by GitHub Actions with `./mvnw -B clean verify` on JDK 21
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(see `.github/workflows/ci.yml`).
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### Expected startup noise
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- On startup the app creates an in-memory **H2** `customers` table with `JdbcTemplate` and logs a few rows — this is
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part of the demo, not an error.
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- It also tries to fetch a random quote from `gturnquist-quoters.cfapps.io`, a demo service that no longer exists.
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The resulting `WARN Could not fetch a quote from ...` is expected and must never fail startup.
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### Prerequisites
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## API
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1) Java sdk
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2) POSTMAN
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All endpoints are served from `http://localhost:8080`.
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### Installing
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| Method | Path | Description |
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| --- | --- | --- |
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| `GET` | `/` | Greeting; accepts an optional `?name=` parameter (defaults to `World`) |
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| `GET` | `/topic` | All topics |
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| `GET` | `/topic/{id}` | A single topic by id |
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| `POST` | `/topic` | Add a topic (JSON body) |
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| `PUT` | `/topic/{id}` | Replace the topic with the given id |
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| `DELETE` | `/topic/{id}` | Delete the topic with the given id |
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| `GET` | `/topic/sort` | All topics sorted by id |
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| `GET` | `/topic/minimum/length/{minLength}` | Topics whose id is longer than `minLength` |
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| `GET` | `/topic/string/operation` | Plain-text dump of the string/stream/regex examples |
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| `GET` | `/topic/file/operation` | Plain-text dump of the NIO.2 file examples |
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| `GET` | `/datetime` | Plain-text dump of the `java.time` examples |
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The topic list lives in memory, so `POST` / `PUT` / `DELETE` changes are lost when the application restarts.
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### Examples
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```bash
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$ curl 'http://localhost:8080/?name=Devin'
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{"id":1,"content":"Hello, Devin!"}
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$ curl http://localhost:8080/topic
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[{"id":"spring","subjectName":"Spring Framework","subjectDescription":"Spring Framework Description"}, ...]
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$ curl -X POST http://localhost:8080/topic \
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-H 'Content-Type: application/json' \
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-d '{"id":"kotlin","subjectName":"Kotlin","subjectDescription":"Kotlin Description"}'
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```
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1) Download or clone
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2) Import the project
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3) Run on location machine
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4) Open Postman, to call API's ( localhost:8080 )
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The `/topic/file/operation` endpoint resolves paths relative to the working directory the application was started
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from, so its output depends on where you run it.
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## Project layout
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```
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src/main/java/hello
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├── Application.java # entry point + CommandLineRunner (H2 seeding, quote fetch)
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├── config/ # RestTemplate bean
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├── controller/ # GreetingController, TopicController, HelloController
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├── declaration/ # CustomPredicate, TimeClient (default/static interface methods)
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├── model/ # Topic, Greeting, Customer, Quote, Value, SimpleTimeClient
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└── service/ # TopicService — where most of the Java 8 examples live
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```
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## Helpful links
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## Helpful Links
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Spring:
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https://spring.io/guides
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Java 8:
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Java 8:
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http://www.baeldung.com/java-8-functional-interfaces
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http://winterbe.com/posts/2015/05/22/java8-concurrency-tutorial-atomic-concurrent-map-examples/
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https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html
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http://winterbe.com/posts/2014/07/31/java8-stream-tutorial-examples/
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http://www.oracle.com/technetwork/articles/java/ma14-java-se-8-streams-2177646.html
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https://docs.oracle.com/javase/tutorial/essential/io/pathOps.html
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https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html
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http://www.baeldung.com/foreach-java
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Java 21:
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http://winterbe.com/posts/2015/03/25/java8-examples-string-number-math-files/
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https://docs.oracle.com/en/java/javase/21/text-blocks/index.html
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http://www.baeldung.com/java-8-comparator-comparing
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https://docs.spring.io/spring-boot/docs/current/reference/html/
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http://www.baeldung.com/java-8-sort-lambda
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## Built with
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https://dzone.com/articles/java-8-friday-goodies-new-new
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## Built With
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* [Maven](https://maven.apache.org/) - Dependency Management
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* [Maven](https://maven.apache.org/) — build and dependency management
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* [Spring Boot](https://spring.io/projects/spring-boot) 3.5.16
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## Authors
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* **Rehman Murad Ali**
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* **Rehman Murad Ali** — original author

‎src/main/java/hello/controller/GreetingController.java‎

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@RestController
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public class GreetingController {
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private static final String template = "Hello, %s!";
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private static final String TEMPLATE = "Hello, %s!";
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private final AtomicLong counter = new AtomicLong();
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@RequestMapping("/")
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public Greeting greeting(@RequestParam(value="name", defaultValue="World") String name) {
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return new Greeting(counter.incrementAndGet(),
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String.format(template, name));
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return new Greeting(counter.incrementAndGet(), TEMPLATE.formatted(name));
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}
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}

‎src/main/java/hello/controller/HelloController.java‎

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import hello.declaration.TimeClient;
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import hello.model.SimpleTimeClient;
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import hello.model.Topic;
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import hello.service.TopicService;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.web.bind.annotation.RestController;
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import org.springframework.web.bind.annotation.RequestMapping;
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import org.springframework.web.bind.annotation.RestController;
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import java.time.LocalDate;
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import java.time.LocalDateTime;
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import java.time.LocalTime;
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import java.time.ZoneId;
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import java.time.chrono.ChronoPeriod;
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import java.time.temporal.ChronoUnit;
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import java.util.List;
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import java.util.regex.Pattern;
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import java.util.stream.Collector;
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import java.util.stream.Collectors;
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@RestController
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public class HelloController {
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String joinTemplate = "Joining All String ID's with JOIN method: ";
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String makeDistinctAndSortCharactersTemplate = "-------------Get all ID characters, select distict and sort with ID= ";
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String splitAllIdWithColonSelectIDWithJavaKeywordThenSortThenJoinTemplate = "-------------Split All Id With Colon," +
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"Select ID With \"Java\" Keyword," +
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" Then Sort Then Join ";
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String findIdHavingCharacterTemplate = "-------------Return All ID having character \'g\' in it: ";
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String findAllFilesInPathAndSortTemplate = "---------Find all files in path and sort: ";
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String findParticularFileInPathAndSortTemplate = "----------Find File in present directory which strats with \"grad\",provided maximum depth=25 and sort : ";
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String findParticularFileInPathAndSortWithWalkFunctionTemplate = "----------Find File in present directory which strats with \"grad\",provided maximum depth=25 and sort : with walk function";
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String readFileWithStreamFunctionTemplate = "---------Read \"temp.txt\" file with stream functions, having \"print\" witin it: ";
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private static final String JOIN_TEMPLATE = "Joining All String ID's with JOIN method: ";
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private static final String MAKE_DISTINCT_AND_SORT_CHARACTERS_TEMPLATE = "-------------Get all ID characters, select distict and sort with ID= ";
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private static final String SPLIT_ALL_ID_WITH_COLON_SELECT_ID_WITH_JAVA_KEYWORD_THEN_SORT_THEN_JOIN_TEMPLATE = """
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-------------Split All Id With Colon,\
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Select ID With "Java" Keyword,\
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Then Sort Then Join\s""";
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private static final String FIND_ID_HAVING_CHARACTER_TEMPLATE = "-------------Return All ID having character 'g' in it: ";
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private static final String FIND_ALL_FILES_IN_PATH_AND_SORT_TEMPLATE = "---------Find all files in path and sort: ";
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private static final String FIND_PARTICULAR_FILE_IN_PATH_AND_SORT_TEMPLATE = "----------Find File in present directory which strats with \"grad\",provided maximum depth=25 and sort : ";
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private static final String FIND_PARTICULAR_FILE_IN_PATH_AND_SORT_WITH_WALK_FUNCTION_TEMPLATE = "----------Find File in present directory which strats with \"grad\",provided maximum depth=25 and sort : with walk function";
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private static final String READ_FILE_WITH_STREAM_FUNCTION_TEMPLATE = "---------Read \"temp.txt\" file with stream functions, having \"print\" witin it: ";
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/** Responses are single line, hence the trailing line-continuation escapes. */
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private static final String LABELLED_SECTIONS_FORMAT = """
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%s%s\
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%s%s\
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%s%s\
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%s%s\
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""";
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@Autowired
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private TopicService topicService;
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@RequestMapping("/datetime")
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public String index() {
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TimeClient myTimeClient = new SimpleTimeClient();
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LocalDateTime localDateTime = LocalDateTime.now();
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return "Greetings from Spring Boot! ----------------------" +
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"Datetime now is " + String.valueOf(myTimeClient.toString()) + "----------------------" +
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"Datetime tomorrow will be " + String.valueOf(myTimeClient.getLocalDateTime().plusDays(1)) + "----------------------" +
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"Datetime of previous month was " + String.valueOf(myTimeClient.getLocalDateTime().minus(1, ChronoUnit.MONTHS)) + "----------------------" +
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"Is this a leap year ? " + String.valueOf(LocalDate.now().isLeapYear()) + "----------------------" +
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"Default system zone id " + String.valueOf(ZoneId.systemDefault()) + "-------------------" +
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"Time in California: " + myTimeClient.getZonedDateTime("Canada/Central").toString();
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return """
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Greetings from Spring Boot! ----------------------\
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Datetime now is %s----------------------\
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Datetime tomorrow will be %s----------------------\
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Datetime of previous month was %s----------------------\
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Is this a leap year ? %s----------------------\
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Default system zone id %s-------------------\
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Time in California: %s\
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""".formatted(
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myTimeClient,
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myTimeClient.getLocalDateTime().plusDays(1),
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myTimeClient.getLocalDateTime().minus(1, ChronoUnit.MONTHS),
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LocalDate.now().isLeapYear(),
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ZoneId.systemDefault(),
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myTimeClient.getZonedDateTime("Canada/Central"));
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}
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/**
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* String Operations in Java 8
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*
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.splitAllIdWithColonSelectIDWithJavaKeywordThenSortThenJoin(join);
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String findIdHavingCharacter = topicService.findIdHavingCharacter();
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return joinTemplate + join
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+ makeDistinctAndSortCharactersTemplate + makeDistinctAndSortCharacters
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+ splitAllIdWithColonSelectIDWithJavaKeywordThenSortThenJoinTemplate + splitAllIdWithColonSelectIDWithJavaKeywordThenSortThenJoin
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+ findIdHavingCharacterTemplate + findIdHavingCharacter;
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return LABELLED_SECTIONS_FORMAT.formatted(
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JOIN_TEMPLATE, join,
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MAKE_DISTINCT_AND_SORT_CHARACTERS_TEMPLATE, makeDistinctAndSortCharacters,
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SPLIT_ALL_ID_WITH_COLON_SELECT_ID_WITH_JAVA_KEYWORD_THEN_SORT_THEN_JOIN_TEMPLATE, splitAllIdWithColonSelectIDWithJavaKeywordThenSortThenJoin,
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FIND_ID_HAVING_CHARACTER_TEMPLATE, findIdHavingCharacter);
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}
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/**
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* File Operation in Java 8
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*
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* @return
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*/
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@RequestMapping("/topic/file/operation")
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String findParticularFileInPathAndSort = topicService.findParticularFileInPathAndSort();
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String findParticularFileInPathAndSortWithWalkFunction = topicService.findParticularFileInPathAndSortWithWalkFunction();
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String readFileWithStreamFunction = topicService.readFileWithStreamFunction();
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return findAllFilesInPathAndSortTemplate + findAllFilesInPathAndSort
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+ findParticularFileInPathAndSortTemplate + findParticularFileInPathAndSort
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+ findParticularFileInPathAndSortWithWalkFunctionTemplate + findParticularFileInPathAndSortWithWalkFunction
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+ readFileWithStreamFunctionTemplate + readFileWithStreamFunction;
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}
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return LABELLED_SECTIONS_FORMAT.formatted(
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FIND_ALL_FILES_IN_PATH_AND_SORT_TEMPLATE, findAllFilesInPathAndSort,
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FIND_PARTICULAR_FILE_IN_PATH_AND_SORT_TEMPLATE, findParticularFileInPathAndSort,
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FIND_PARTICULAR_FILE_IN_PATH_AND_SORT_WITH_WALK_FUNCTION_TEMPLATE, findParticularFileInPathAndSortWithWalkFunction,
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READ_FILE_WITH_STREAM_FUNCTION_TEMPLATE, readFileWithStreamFunction);
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}
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}

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