// Handle successful response
        response.getItems().forEach(item -> 
            System.out.println("Async suggestion: " + item.getText()[0])
        );
    })
    .error(throwable -> {
        // Handle error
        System.err.println("Error: " + throwable.getMessage());
    });
```

## Advanced Usage

### Index from Existing Documents

```java

- **Comprehensive Content Extraction**: Office documents, PDFs, archives, images, audio/video files
- **Multi-Threading**: Configurable thread pools for high-performance crawling
- **Fault Tolerance**: Built-in retry mechanisms and error handling
- **Flexible Configuration**: XML-based dependency injection with LastaFlute DI
- **Extensible Architecture**: Plugin system for custom extractors, transformers, and clients