Data Input and Output

/**
 * Create DataSet from Java collection
 * @param data the collection to create DataSet from
 * @return DataSet containing collection elements
 */
public <T> DataSet<T> fromCollection(Collection<T> data);

/**
 * Create DataSet from individual elements
 * @param data the elements to include in the DataSet
 * @return DataSet containing the specified elements
 */
@SafeVarargs
public final <T> DataSet<T> fromElements(T... data);

/**
 * Read text file line by line
 * @param filePath path to the text file
 * @return DataSet where each element is a line from the file
 */
public DataSet<String> readTextFile(String filePath);

/**
 * Read text file line by line with specific character encoding
 * @param filePath path to the text file
 * @param charsetName the charset name for decoding the file
 * @return DataSet where each element is a line from the file
 */
public DataSet<String> readTextFile(String filePath, String charsetName);

/**
 * Read text file as StringValue objects
 * @param filePath path to the text file
 * @return DataSet where each element is a StringValue from the file
 */
public DataSource<StringValue> readTextFileWithValue(String filePath);

/**
 * Read text file as StringValue objects with charset and error handling
 * @param filePath path to the text file
 * @param charsetName the charset name for decoding the file
 * @param skipInvalidLines whether to skip lines that cannot be decoded
 * @return DataSet where each element is a StringValue from the file
 */
public DataSource<StringValue> readTextFileWithValue(String filePath, String charsetName, boolean skipInvalidLines);

/**
 * Read file containing primitive values
 * @param filePath path to the file
 * @param typeClass the class of the primitive type
 * @return DataSet with elements of the primitive type
 */
public <X> DataSource<X> readFileOfPrimitives(String filePath, Class<X> typeClass);

/**
 * Read file containing primitive values with custom delimiter
 * @param filePath path to the file
 * @param delimiter the delimiter separating values
 * @param typeClass the class of the primitive type
 * @return DataSet with elements of the primitive type
 */
public <X> DataSource<X> readFileOfPrimitives(String filePath, String delimiter, Class<X> typeClass);

/**
 * Read file using custom input format
 * @param inputFormat the input format to use for reading
 * @param filePath path to the file
 * @return DataSet with elements read by the input format
 */
public <T> DataSet<T> readFile(FileInputFormat<T> inputFormat, String filePath);

/**
 * Generate sequence of numbers
 * @param from starting number (inclusive)
 * @param to ending number (inclusive)  
 * @return DataSet containing the number sequence
 */
public DataSet<Long> generateSequence(long from, long to);

// From collection
List<String> words = Arrays.asList("hello", "world", "flink");
DataSet<String> wordsDataSet = env.fromCollection(words);

// From elements
DataSet<Integer> numbers = env.fromElements(1, 2, 3, 4, 5);

// Read text file
DataSet<String> textData = env.readTextFile("/path/to/input.txt");

// Generate sequence
DataSet<Long> sequence = env.generateSequence(1, 1000);

/**
 * Create CSV reader for structured data reading
 * @param filePath path to the CSV file
 * @return CsvReader for configuration and DataSet creation
 */
public CsvReader readCsvFile(String filePath);

/**
 * CSV reader with configuration options
 */
public class CsvReader {
    /**
     * Set line delimiter (default: newline)
     * @param delimiter the line delimiter
     * @return CsvReader for method chaining
     */
    public CsvReader lineDelimiter(String delimiter);
    
    /**
     * Set field delimiter (default: comma)  
     * @param delimiter the field delimiter
     * @return CsvReader for method chaining
     */
    public CsvReader fieldDelimiter(String delimiter);
    
    /**
     * Include only specific fields by position
     * @param fields boolean array indicating which fields to include
     * @return CsvReader for method chaining
     */
    public CsvReader includeFields(boolean... fields);
    
    /**
     * Ignore the first line (header row)
     * @return CsvReader for method chaining
     */
    public CsvReader ignoreFirstLine();
    
    /**
     * Ignore lines that cannot be parsed
     * @return CsvReader for method chaining
     */
    public CsvReader ignoreInvalidLines();
    
    /**
     * Parse CSV into POJO objects
     * @param pojoType the POJO class type
     * @param pojoFields the field names in order
     * @return DataSource of POJO objects
     */
    public <T> DataSource<T> pojoType(Class<T> pojoType, String... pojoFields);
    
    /**
     * Parse CSV with specified field types
     * @param fieldTypes the types for each field
     * @return DataSource with typed tuples
     */
    public DataSource<?> types(Class<?>... fieldTypes);
}

// Basic CSV reading
DataSet<Tuple3<String, Integer, Double>> csvData = env
    .readCsvFile("/path/to/data.csv")
    .fieldDelimiter(",")
    .lineDelimiter("\n")
    .ignoreFirstLine()
    .types(String.class, Integer.class, Double.class);

// CSV to POJO
public static class Person {
    public String name;
    public Integer age;
    public String city;
}

DataSet<Person> people = env
    .readCsvFile("/path/to/people.csv")
    .ignoreFirstLine()
    .pojoType(Person.class, "name", "age", "city");

// Selective field reading
DataSet<Tuple2<String, Integer>> nameAge = env
    .readCsvFile("/path/to/people.csv")
    .includeFields(true, true, false) // name, age, skip city
    .types(String.class, Integer.class);

/**
 * Input format for reading text files line by line
 */
public class TextInputFormat extends FileInputFormat<String> {
    // Reads text files, each line becomes a String element
}

/**
 * Input format for reading text files as StringValue objects  
 */
public class TextValueInputFormat extends FileInputFormat<StringValue> {
    // Reads text files as StringValue for better memory efficiency
}

/**
 * Input format for reading from Java collections
 */
public class CollectionInputFormat<T> implements InputFormat<T, GenericInputSplit> {
    /**
     * Create input format from collection
     * @param dataSet the collection to read from
     * @param serializer serializer for the data type
     */
    public CollectionInputFormat(Collection<T> dataSet, TypeSerializer<T> serializer);
}

/**
 * Input format for reading from iterators
 */
public class IteratorInputFormat<T> implements InputFormat<T, GenericInputSplit> {
    /**
     * Create input format from iterator
     * @param iterator the iterator to read from
     * @param serializer serializer for the data type
     */
    public IteratorInputFormat(Iterator<T> iterator, TypeSerializer<T> serializer);
}

/**
 * Input format for reading primitive types
 */
public class PrimitiveInputFormat<T> extends FileInputFormat<T> {
    /**
     * Create input format for primitive types
     * @param filePath path to the file
     * @param delimiter delimiter between values
     * @param typeClass the primitive type class
     */
    public PrimitiveInputFormat(Path filePath, String delimiter, Class<T> typeClass);
}

/**
 * CSV input format for Row objects
 */
public class RowCsvInputFormat extends CsvInputFormat<Row> {
    // Specialized CSV format for Row-based data
}

/**
 * Write DataSet as text file
 * @param filePath path where to write the file
 * @return DataSink for execution
 */
public DataSink<T> writeAsText(String filePath);

/**
 * Write DataSet as text file with write mode
 * @param filePath path where to write the file  
 * @param writeMode OVERWRITE or NO_OVERWRITE
 * @return DataSink for execution
 */
public DataSink<T> writeAsText(String filePath, WriteMode writeMode);

/**
 * Write DataSet as CSV file
 * @param filePath path where to write the CSV file
 * @return DataSink for execution
 */
public DataSink<T> writeAsCsv(String filePath);

/**
 * Write with custom text formatter
 * @param filePath path where to write the file
 * @param formatter custom text formatter
 * @return DataSink for execution
 */
public DataSink<T> writeAsFormattedText(String filePath, TextFormatter<T> formatter);

/**
 * Write using custom output format
 * @param outputFormat the output format to use
 * @param filePath path where to write
 * @return DataSink for execution
 */
public DataSink<T> write(OutputFormat<T> outputFormat, String filePath);

/**
 * Output using custom output format (no file path)
 * @param outputFormat the output format to use
 * @return DataSink for execution
 */
public DataSink<T> output(OutputFormat<T> outputFormat);

/**
 * Print DataSet content to standard output (executes immediately)
 * @throws Exception if printing fails
 */
public void print() throws Exception;

/**
 * Print DataSet content to standard error (executes immediately)
 * @throws Exception if printing fails
 */
public void printToErr() throws Exception;

/**
 * Print DataSet content with identifier to standard output
 * @param sinkIdentifier identifier for the print sink
 * @return DataSink for execution
 */
public DataSink<T> print(String sinkIdentifier);

/**
 * Print DataSet content with identifier to standard error
 * @param sinkIdentifier identifier for the print sink
 * @return DataSink for execution
 */
public DataSink<T> printToErr(String sinkIdentifier);

/**
 * Print DataSet content on task manager with prefix (for debugging)
 * @param prefix prefix for the printed output
 * @return DataSink for execution
 */
public DataSink<T> printOnTaskManager(String prefix);

// Write as text
DataSet<String> result = processedData;
result.writeAsText("/path/to/output.txt", WriteMode.OVERWRITE);

// Write as CSV
DataSet<Tuple3<String, Integer, Double>> data = getData();
data.writeAsCsv("/path/to/output.csv");

// Print for debugging
result.print();

// Custom formatter
result.writeAsFormattedText("/path/to/formatted.txt", new TextFormatter<String>() {
    @Override
    public String format(String record) {
        return "Record: " + record;
    }
});

/**
 * Output format for writing text files
 */
public class TextOutputFormat<T> extends FileOutputFormat<T> {
    /**
     * Create text output format
     * @param outputPath path to write the output
     */
    public TextOutputFormat(Path outputPath);
}

/**
 * Output format for writing CSV files
 */
public class CsvOutputFormat<T> extends FileOutputFormat<T> {
    /**
     * Create CSV output format
     * @param outputPath path to write the CSV
     */
    public CsvOutputFormat(Path outputPath);
    
    /**
     * Set field delimiter
     * @param fieldDelimiter delimiter between fields
     */
    public void setFieldDelimiter(String fieldDelimiter);
    
    /**
     * Set record delimiter  
     * @param recordDelimiter delimiter between records
     */
    public void setRecordDelimiter(String recordDelimiter);
}

/**
 * Output format for printing to stdout/stderr
 */
public class PrintingOutputFormat<T> implements OutputFormat<T> {
    /**
     * Create printing output format
     * @param targetStream target stream (System.out or System.err)
     * @param sinkIdentifier identifier for the sink
     */
    public PrintingOutputFormat(PrintStream targetStream, String sinkIdentifier);
}

/**
 * Output format for collecting to local collection
 */
public class LocalCollectionOutputFormat<T> implements OutputFormat<T> {
    /**
     * Create local collection output format
     * @param out the collection to write to
     */
    public LocalCollectionOutputFormat(List<T> out);
}

/**
 * Output format that discards all records (for testing)
 */
public class DiscardingOutputFormat<T> implements OutputFormat<T> {
    // Discards all records - useful for performance testing
}

/**
 * Write mode for file operations
 */
public enum WriteMode {
    /** Overwrite existing files */
    OVERWRITE,
    /** Fail if file already exists */
    NO_OVERWRITE
}

/**
 * Properties for data splits
 */
public class SplitDataProperties<T> {
    /**
     * Specify that data is sorted by given fields
     * @param fields the fields by which data is sorted
     * @return configured properties
     */
    public SplitDataProperties<T> splitsPartitionedBy(int... fields);
    
    /**
     * Specify grouping properties
     * @param fields the fields by which data is grouped
     * @return configured properties
     */
    public SplitDataProperties<T> splitsGroupedBy(int... fields);
}

import org.apache.flink.api.java.io.*;
import org.apache.flink.api.java.operators.DataSource;
import org.apache.flink.api.java.operators.DataSink;
import org.apache.flink.api.common.io.FileInputFormat;
import org.apache.flink.api.common.io.FileOutputFormat;
import org.apache.flink.api.common.io.InputFormat;
import org.apache.flink.api.common.io.OutputFormat;
import org.apache.flink.core.fs.FileSystem.WriteMode;
import org.apache.flink.types.StringValue;
import org.apache.flink.types.Row;
import java.util.Collection;
import java.util.List;