# Io / Github / Biezhi / Java11 / Files

## Overview

This module appears to be a small Java 11 file-IO example that demonstrates the `Files` API for working with text files. The implementation in [src/main/java/io/github/biezhi/java11/files/Example.java](src/main/java/io/github/biezhi/java11/files/Example.java) shows a complete write-read-delete cycle against a local file, likely intended as a simple reference for how to use the newer convenience methods added in JDK 11.

For a new engineer, the main value of the module is that it shows the happy path for basic file operations in a compact, easy-to-run form: create content, persist it, verify the contents round-trip correctly, and then clean up the temporary file.

## Key Classes and Interfaces

### [Example](src/main/java/io/github/biezhi/java11/files/Example.java)

This is the only class in the module, and it acts as an executable demo rather than a reusable library component. Its role is to show how `java.nio.file.Files` and `java.nio.file.Paths` can be combined to write a string to disk, read it back, compare the result, and delete the file afterward.

#### `main(String[] args)`

- **Purpose:** Runs the full file lifecycle example.
- **Parameters:** Accepts the standard `String[] args`, but the implementation does not use them.
- **Returns:** `void`
- **Throws:** Declares `throws Exception`, so any file-system failure will propagate to the caller.
- **Behavior:**
  1. Defines a string literal: `"Hello biezhi."`
  2. Writes that string to `hello.txt` using `Files.writeString(Paths.get("hello.txt"), text)`.
  3. Reads the file back using `Files.readString(Paths.get("hello.txt"))`.
  4. Prints whether the original and read values are equal.
  5. Deletes `hello.txt` using `Files.delete(Paths.get("hello.txt"))`.

The method is intentionally linear and side-effect driven. It does not encapsulate error handling, path management, or cleanup logic beyond the final delete call.

## How It Works

The module follows a simple three-step flow:

1. **Create content in memory.**
   - `text` holds the string that will be written to disk.

2. **Persist and verify the file contents.**
   - `Files.writeString(...)` writes the string to a file named `hello.txt` in the current working directory.
   - `Files.readString(...)` reads the same file back into memory.
   - `System.out.println(text.equals(readText))` prints `true` if the round trip preserved the exact content.

3. **Clean up the temporary file.**
   - `Files.delete(...)` removes `hello.txt` after the verification step completes.

### Relationship to the JDK API

This module is effectively a usage example for the Java NIO file API:

- `Paths.get("hello.txt")` converts a simple file name into a `Path`.
- `Files.writeString(...)` and `Files.readString(...)` provide concise text-based operations.
- `Files.delete(...)` removes the file when the demo is done.

The code is intentionally minimal so the file API behavior is easy to see without additional abstraction layers.

## Mermaid Diagram

```mermaid
flowchart LR
Module["io.github.biezhi.java11.files.Example"] --> Main["main(String[] args)"]
Main --> Write["Files.writeString to hello.txt"]
Main --> Read["Files.readString from hello.txt"]
Main --> Compare["Print equality check"]
Main --> Delete["Files.delete hello.txt"]
```

## Dependencies and Integration

### JDK APIs

The module depends only on standard Java classes:

- [java.nio.file.Files](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/Files.html) through direct use in [Example](src/main/java/io/github/biezhi/java11/files/Example.java)
- [java.nio.file.Paths](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/Paths.html) through direct use in [Example](src/main/java/io/github/biezhi/java11/files/Example.java)

### External integration

There are no package-level dependencies or cross-module relationships recorded for this module. The class operates entirely on the local filesystem in the current working directory.

## Notes for Developers

- The example writes to a hard-coded file name, `hello.txt`, so running it will create and then delete a file in the process working directory.
- The method throws `Exception` instead of handling I/O failures locally. That keeps the demo concise, but production code would usually narrow the exception type and add error handling.
- Because the delete step is unconditional and not wrapped in a `try/finally`, a failure earlier in the method can leave `hello.txt` behind.
- The module is a demo, not a utility package. If you extend it, keep the sample focused on illustrating a single file-system concept at a time.

## Related Source

- [src/main/java/io/github/biezhi/java11/files/Example.java](src/main/java/io/github/biezhi/java11/files/Example.java)