Content Type Detection

/**
 * Interface for detecting the media type of documents
 */
public interface Detector {
    /**
     * Detects the media type of the given document
     * @param input Input stream containing document data (may be null)
     * @param metadata Metadata containing hints like filename or content type
     * @return MediaType representing the detected content type
     * @throws IOException If an I/O error occurs during detection
     */
    MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Default composite detector combining multiple detection strategies
 */
public class DefaultDetector extends CompositeDetector {
    /**
     * Creates a DefaultDetector with standard detection strategies
     */
    public DefaultDetector();
    
    /**
     * Creates a DefaultDetector with custom MIME types registry
     * @param types MimeTypes registry for magic number detection
     */
    public DefaultDetector(MimeTypes types);
    
    /**
     * Creates a DefaultDetector with custom class loader for service discovery
     * @param loader ClassLoader for discovering detector services
     */
    public DefaultDetector(ClassLoader loader);
    
    /**
     * Creates a DefaultDetector with custom types and class loader
     * @param types MimeTypes registry for magic number detection
     * @param loader ClassLoader for discovering detector services
     */
    public DefaultDetector(MimeTypes types, ClassLoader loader);
}

import org.apache.tika.detect.DefaultDetector;
import org.apache.tika.detect.Detector;
import org.apache.tika.metadata.Metadata;
import org.apache.tika.mime.MediaType;
import java.io.FileInputStream;
import java.io.InputStream;

// Basic content type detection
Detector detector = new DefaultDetector();
Metadata metadata = new Metadata();
metadata.set(Metadata.RESOURCE_NAME_KEY, "document.pdf");

try (InputStream stream = new FileInputStream("document.pdf")) {
    MediaType mediaType = detector.detect(stream, metadata);
    System.out.println("Detected type: " + mediaType.toString());
}

// Detection from filename only
Metadata filenameMetadata = new Metadata();
filenameMetadata.set(Metadata.RESOURCE_NAME_KEY, "spreadsheet.xlsx");
MediaType typeFromName = detector.detect(null, filenameMetadata);

/**
 * Detector that combines multiple detection strategies
 */
public class CompositeDetector implements Detector {
    /**
     * Creates a CompositeDetector with the specified detectors
     * @param detectors List of detectors to combine, applied in order
     */
    public CompositeDetector(List<Detector> detectors);
    
    /**
     * Creates a CompositeDetector with the specified detectors
     * @param detectors Array of detectors to combine, applied in order
     */
    public CompositeDetector(Detector... detectors);
    
    /**
     * Gets the list of detectors used by this composite
     * @return List of Detector instances in application order
     */
    public List<Detector> getDetectors();
}

/**
 * Detector based on file extensions and naming patterns
 */
public class TypeDetector implements Detector {
    /**
     * Creates a TypeDetector with default MIME types registry
     */
    public TypeDetector();
    
    /**
     * Creates a TypeDetector with custom MIME types registry
     * @param types MimeTypes registry containing type mappings
     */
    public TypeDetector(MimeTypes types);
    
    /**
     * Detects media type based on filename extension
     * @param input Input stream (ignored by this detector)
     * @param metadata Metadata containing filename information
     * @return MediaType based on file extension, or OCTET_STREAM if unknown
     */
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Detector based on filename patterns and heuristics
 */
public class NameDetector implements Detector {
    /**
     * Creates a NameDetector with default configuration
     */
    public NameDetector();
    
    /**
     * Detects media type based on filename patterns
     * @param input Input stream (not used by this detector)
     * @param metadata Metadata containing filename or resource name
     * @return MediaType based on filename analysis
     */
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Detector for identifying text content and formats
 */
public class TextDetector implements Detector {
    /**
     * Creates a TextDetector with default configuration
     */
    public TextDetector();
    
    /**
     * Detects text content types and formats
     * @param input Input stream containing potential text data
     * @param metadata Metadata with additional hints
     * @return MediaType for detected text format
     */
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Detector using magic numbers and byte signatures
 */
public class MagicDetector implements Detector {
    /**
     * Creates a MagicDetector with default MIME types registry
     */
    public MagicDetector();
    
    /**
     * Creates a MagicDetector with custom MIME types registry
     * @param types MimeTypes registry containing magic patterns
     */
    public MagicDetector(MimeTypes types);
    
    /**
     * Detects media type using magic number analysis
     * @param input Input stream to analyze for magic patterns
     * @param metadata Metadata (may provide additional context)
     * @return MediaType based on magic number detection
     */
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Interface for detecting character encodings
 */
public interface EncodingDetector {
    /**
     * Detects the character encoding of the given text stream
     * @param input Input stream containing text data
     * @param metadata Metadata with encoding hints
     * @return Charset representing the detected encoding, or null if unknown
     * @throws IOException If an I/O error occurs during detection
     */
    Charset detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Default character encoding detector
 */
public class DefaultEncodingDetector implements EncodingDetector {
    /**
     * Creates a DefaultEncodingDetector with standard detection algorithms
     */
    public DefaultEncodingDetector();
    
    /**
     * Detects character encoding using multiple strategies
     * @param input Input stream containing text data
     * @param metadata Metadata containing encoding hints
     * @return Charset representing detected encoding
     */
    public Charset detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Reader with automatic encoding detection
 */
public class AutoDetectReader extends Reader {
    /**
     * Creates an AutoDetectReader for the given input stream
     * @param input Input stream containing text data
     */
    public AutoDetectReader(InputStream input);
    
    /**
     * Creates an AutoDetectReader with custom encoding detector
     * @param input Input stream containing text data
     * @param detector EncodingDetector to use for encoding detection
     */
    public AutoDetectReader(InputStream input, EncodingDetector detector);
    
    /**
     * Creates an AutoDetectReader with metadata hints
     * @param input Input stream containing text data
     * @param metadata Metadata containing encoding hints
     */
    public AutoDetectReader(InputStream input, Metadata metadata);
    
    /**
     * Gets the detected character encoding
     * @return Charset representing the detected encoding
     */
    public Charset getCharset();
}

/**
 * Interface for trained detection models
 */
public interface TrainedModel {
    /**
     * Predicts content type using the trained model
     * @param input Byte array containing document data
     * @return Probability distribution over content types
     */
    float[] predict(byte[] input);
    
    /**
     * Gets the content types supported by this model
     * @return Array of MediaType objects supported by the model
     */
    MediaType[] getSupportedTypes();
}

/**
 * Neural network-based trained model implementation
 */
public class NNTrainedModel implements TrainedModel {
    /**
     * Creates an NNTrainedModel from model data
     * @param modelData Byte array containing the trained model
     */
    public NNTrainedModel(byte[] modelData);
    
    /**
     * Loads a model from resources
     * @param modelPath Path to model resource
     * @return NNTrainedModel instance
     */
    public static NNTrainedModel loadFromResource(String modelPath);
}

/**
 * Detector using neural network models
 */
public class NNExampleModelDetector implements Detector {
    /**
     * Creates an NN detector with default model
     */
    public NNExampleModelDetector();
    
    /**
     * Creates an NN detector with custom model
     * @param model TrainedModel to use for detection
     */
    public NNExampleModelDetector(TrainedModel model);
}

/**
 * Detector for empty files
 */
public class EmptyDetector implements Detector {
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Detector that can override other detectors based on metadata
 */
public class OverrideDetector implements Detector {
    public OverrideDetector(Detector originalDetector);
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Detector for zero-byte files
 */
public class ZeroSizeFileDetector implements Detector {
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Detector using system file command (Unix/Linux)
 */
public class FileCommandDetector implements Detector {
    public FileCommandDetector();
    public boolean isAvailable();
    public MediaType detect(InputStream input, Metadata metadata) throws IOException;
}

/**
 * Statistical analysis of text content
 */
public class TextStatistics {
    /**
     * Analyzes text statistics from input stream
     * @param input Input stream containing text data
     * @return TextStatistics object with analysis results
     */
    public static TextStatistics calculate(InputStream input) throws IOException;
    
    /**
     * Gets the percentage of printable characters
     * @return Percentage (0.0 to 1.0) of printable characters
     */
    public double getPrintableRatio();
    
    /**
     * Gets the average line length
     * @return Average number of characters per line
     */
    public double getAverageLineLength();
    
    /**
     * Determines if content appears to be text
     * @return true if content appears to be text
     */
    public boolean isText();
}

// Create custom detector chain
List<Detector> detectors = Arrays.asList(
    new MagicDetector(),           // Prioritize magic numbers
    new TypeDetector(),            // Fall back to filename
    new NNExampleModelDetector(),  // Use ML for ambiguous cases
    new EmptyDetector()            // Handle empty files
);

CompositeDetector customDetector = new CompositeDetector(detectors);