DataSet Operations

/**
 * Abstract class representing a distributed dataset of elements of type T
 * @param <T> the type of elements in the dataset
 */
public abstract class DataSet<T> {
    // Core transformation and output methods
}

/**
 * Apply a map function to each element
 * @param mapper the map function to apply
 * @return MapOperator for further configuration
 */
public <R> MapOperator<T, R> map(MapFunction<T, R> mapper);

/**
 * Apply a map function to each partition
 * @param mapper the map function to apply to each partition
 * @return MapPartitionOperator for further configuration
 */
public <R> MapPartitionOperator<T, R> mapPartition(MapPartitionFunction<T, R> mapper);

// Simple map transformation
DataSet<String> words = env.fromElements("hello", "world");
DataSet<Integer> lengths = words.map(new MapFunction<String, Integer>() {
    @Override
    public Integer map(String value) {
        return value.length();
    }
});

// Using lambda expression (Java 8+)
DataSet<String> uppercase = words.map(String::toUpperCase);

// Map partition for batch processing
DataSet<String> processed = words.mapPartition(new MapPartitionFunction<String, String>() {
    @Override
    public void mapPartition(Iterable<String> values, Collector<String> out) {
        for (String value : values) {
            out.collect(value.trim().toLowerCase());
        }
    }
});

/**
 * Apply a flatMap function to each element
 * @param flatter the flatMap function to apply
 * @return FlatMapOperator for further configuration
 */
public <R> FlatMapOperator<T, R> flatMap(FlatMapFunction<T, R> flatter);

// Split sentences into words
DataSet<String> sentences = env.fromElements("hello world", "flink java");
DataSet<String> words = sentences.flatMap(new FlatMapFunction<String, String>() {
    @Override
    public void flatMap(String sentence, Collector<String> out) {
        for (String word : sentence.split(" ")) {
            out.collect(word);
        }
    }
});

/**
 * Filter elements based on a predicate
 * @param filter the filter predicate
 * @return FilterOperator for further configuration
 */
public FilterOperator<T> filter(FilterFunction<T> filter);

// Filter words longer than 4 characters
DataSet<String> words = env.fromElements("hello", "hi", "world", "a");
DataSet<String> longWords = words.filter(new FilterFunction<String>() {
    @Override
    public boolean filter(String value) {
        return value.length() > 4;
    }
});

// Using lambda expression
DataSet<String> filtered = words.filter(word -> word.startsWith("h"));

/**
 * Reduce the DataSet using a reduce function
 * @param reducer the reduce function
 * @return ReduceOperator for further configuration
 */
public ReduceOperator<T> reduce(ReduceFunction<T> reducer);

/**
 * Apply a reduce function to grouped elements
 * @param reducer the group reduce function
 * @return GroupReduceOperator for further configuration
 */
public <R> GroupReduceOperator<T, R> reduceGroup(GroupReduceFunction<T, R> reducer);

/**
 * Remove duplicate elements
 * @return DistinctOperator for further configuration
 */
public DistinctOperator<T> distinct();

/**
 * Remove duplicates based on key fields
 * @param fields the field positions for duplicate detection
 * @return DistinctOperator for further configuration
 */
public DistinctOperator<T> distinct(int... fields);

/**
 * Remove duplicates based on key selector
 * @param keyExtractor function to extract the key for comparison
 * @return DistinctOperator for further configuration
 */
public <K> DistinctOperator<T> distinct(KeySelector<T, K> keyExtractor);

/**
 * Union with another DataSet
 * @param other the other DataSet to union with
 * @return UnionOperator containing elements from both DataSets
 */
public UnionOperator<T> union(DataSet<T> other);

/**
 * Group by field positions (for Tuple types)
 * @param fields the field positions to group by
 * @return UnsortedGrouping for further operations
 */
public UnsortedGrouping<T> groupBy(int... fields);

/**
 * Group by field names (for POJO types)
 * @param fields the field names to group by
 * @return UnsortedGrouping for further operations
 */
public UnsortedGrouping<T> groupBy(String... fields);

/**
 * Group by key selector function
 * @param keyExtractor function to extract the grouping key
 * @return UnsortedGrouping for further operations
 */
public <K> UnsortedGrouping<T> groupBy(KeySelector<T, K> keyExtractor);

/**
 * Partition by hash of specified fields
 * @param fields the fields to use for hash partitioning
 * @return PartitionOperator for further configuration
 */
public PartitionOperator<T> partitionByHash(int... fields);

/**
 * Partition by range of specified fields
 * @param fields the fields to use for range partitioning
 * @return PartitionOperator for further configuration
 */
public PartitionOperator<T> partitionByRange(int... fields);

/**
 * Sort partition by specified field and order
 * @param field the field to sort by
 * @param order the sort order (ASCENDING or DESCENDING)
 * @return SortPartitionOperator for further configuration
 */
public SortPartitionOperator<T> sortPartition(int field, Order order);

/**
 * Project specified fields (for Tuple types)
 * @param fieldIndexes the field indexes to project
 * @return ProjectOperator with projected fields
 */
public ProjectOperator<T, ?> project(int... fieldIndexes);

/**
 * Collect all elements to the driver program
 * @return List containing all elements
 * @throws Exception if collection fails
 */
public List<T> collect() throws Exception;

/**
 * Get the first n elements
 * @param n number of elements to retrieve
 * @return DataSet containing first n elements
 */
public DataSet<T> first(int n);

/**
 * Count the number of elements
 * @return the number of elements in the DataSet
 * @throws Exception if counting fails
 */
public long count() throws Exception;

/**
 * Sample elements from the DataSet
 * @param withReplacement whether to sample with replacement
 * @param fraction the fraction of elements to sample
 * @return DataSet with sampled elements
 */
public DataSet<T> sample(boolean withReplacement, double fraction);

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

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

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

/**
 * Print to standard output
 * @return DataSink for execution
 */
public DataSink<T> print();

/**
 * Print to standard error
 * @return DataSink for execution
 */
public DataSink<T> printToErr();

/**
 * Get the type information for this DataSet
 * @return TypeInformation describing the element type
 */
public TypeInformation<T> getType();

/**
 * Get the execution environment
 * @return ExecutionEnvironment that created this DataSet
 */
public ExecutionEnvironment getExecutionEnvironment();

import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.operators.*;
import org.apache.flink.api.common.functions.*;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.util.Collector;
import org.apache.flink.core.fs.FileSystem.WriteMode;