fix: Fix lint errors in java/custom_java_impl project

[Skyllarr]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @Skyllarr, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on a comprehensive refactor to align the Java codebase with established linting rules and best practices. The changes are purely cosmetic and aimed at improving code maintainability, consistency, and documentation without altering any existing functionality. It ensures the project adheres to high-quality coding standards, making it easier for developers to understand and contribute to the codebase.

Highlights

• Code Style and Readability Improvements: The pull request introduces various changes to enhance code style and readability, including standardizing Javadoc comments, adding the 'final' keyword to method parameters, and replacing magic numbers with named constants.
• Consistent Import Statements: Wildcard imports have been replaced with explicit class imports across the codebase, improving clarity and reducing potential naming conflicts.
• Introduction of Package-Level Documentation: New 'package-info.java' files have been added to both client and server packages, providing comprehensive package-level Javadoc documentation.

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[gemini-code-assist]

Code Review

This pull request does a good job of fixing lint errors and improving code quality by adding documentation, using constants, and making parameters final. I've found a few areas for further improvement, including a critical issue with the streaming implementation that doesn't actually stream, and some opportunities to reduce code duplication and improve error handling.

[gemini-code-assist]

The sendTaskStreaming method's name is misleading as it doesn't actually stream the response. HttpResponse.BodyHandlers.ofString() is a blocking handler that buffers the entire response body in memory before returning. This defeats the purpose of a streaming API, especially for long-running tasks that produce many updates.

To implement true streaming, you should use a non-blocking body handler like HttpResponse.BodyHandlers.ofLines(), which provides a Stream<String> that can be processed as data arrives. This would require refactoring the subsequent parsing logic.

[gemini-code-assist]

There is code duplication in the constructors for initializing baseUrl and objectMapper. You can simplify this by using constructor chaining, where one constructor calls another. This improves maintainability by centralizing the initialization logic.

    public A2AClient(final String url) {
        this(url, HttpClient.newBuilder()
                .connectTimeout(Duration.ofSeconds(CONNECTION_TIMEOUT_SECONDS))
                .build());
    }
    
    /**
     * Create a new A2A client with custom HTTP client.
     *
     * @param url the base URL of the A2A server
     * @param client custom HTTP client
     */
    public A2AClient(final String url, final HttpClient client) {
        this.baseUrl = url.endsWith("/")
                ? url.substring(0, url.length() - 1) : url;
        this.httpClient = client;
        this.objectMapper = new ObjectMapper();
    }

[gemini-code-assist]

In this catch block, you're catching a generic Exception and only passing e.getMessage() to sendErrorEvent. This practice can hide important details for debugging, such as the stack trace and the original exception type. For better error diagnostics, it's recommended to log the full exception. If a logger is not available, consider enhancing sendErrorEvent to include more error details in the response, at least during development.