Javadoc is the correct tool used to generate API documentation in HTML format from doc comments in source code.

Javadoc Tool:
Javadoc is a documentation generator tool provided by the Java Development Kit (JDK). It extracts documentation comments written in a specific format from Java source code files and generates API documentation in HTML format. The Javadoc tool comes bundled with the JDK and is available for use without the need for any additional installations.

Key Features of Javadoc Tool:
1. Doc Comments: Javadoc tool extracts specially formatted comments known as doc comments from Java source code files. These doc comments contain information about the code, such as class or interface descriptions, method summaries, parameter details, return values, exceptions, etc.

2. HTML Documentation: Javadoc processes the doc comments and generates API documentation in HTML format. HTML documentation is platform-independent and can be easily viewed in any web browser.

3. Class Hierarchy: Javadoc also generates a class hierarchy diagram, which shows the relationships between classes and interfaces in the codebase. This diagram helps developers understand the structure and inheritance relationships within the codebase.

4. Cross-Referencing: Javadoc provides cross-referencing capabilities by linking different parts of the documentation together. It automatically generates links to related classes, methods, fields, and other elements, allowing users to navigate through the documentation seamlessly.

5. Customization Options: Javadoc offers various customization options to control the content and appearance of the generated documentation. Developers can use tags and annotations to enhance the generated documentation with additional information, such as code examples, usage guidelines, and implementation details.

Conclusion:
In summary, the Javadoc tool is used to generate API documentation in HTML format from doc comments in source code. It is a powerful tool that simplifies the process of documenting Java code and makes it easier for developers to understand and use APIs.