Utility Functions

/**
 * Utility class for handling program parameters
 */
public class ParameterTool implements Serializable {
    
    /**
     * Create ParameterTool from command line arguments
     * @param args command line arguments in key-value format
     * @return ParameterTool instance
     */
    public static ParameterTool fromArgs(String[] args);
    
    /**
     * Create ParameterTool from properties file
     * @param path path to the properties file
     * @return ParameterTool instance
     * @throws IOException if file cannot be read
     */
    public static ParameterTool fromPropertiesFile(String path) throws IOException;
    
    /**
     * Create ParameterTool from properties file with ClassLoader
     * @param file properties file
     * @param classLoader class loader to use
     * @return ParameterTool instance
     * @throws IOException if file cannot be read
     */
    public static ParameterTool fromPropertiesFile(File file, ClassLoader classLoader) throws IOException;
    
    /**
     * Create ParameterTool from Map
     * @param map map containing key-value pairs
     * @return ParameterTool instance
     */
    public static ParameterTool fromMap(Map<String, String> map);
    
    /**
     * Create ParameterTool from system properties
     * @return ParameterTool instance with system properties
     */
    public static ParameterTool fromSystemProperties();
    
    /**
     * Get parameter value as String
     * @param key parameter key
     * @return parameter value or null if not found
     */
    public String get(String key);
    
    /**
     * Get parameter value with default
     * @param key parameter key
     * @param defaultValue default value if key not found
     * @return parameter value or default value
     */
    public String get(String key, String defaultValue);
    
    /**
     * Get parameter value as integer
     * @param key parameter key
     * @return parameter value as integer
     * @throws NumberFormatException if value is not a valid integer
     */
    public int getInt(String key);
    
    /**
     * Get parameter value as integer with default
     * @param key parameter key
     * @param defaultValue default value if key not found
     * @return parameter value as integer or default value
     */
    public int getInt(String key, int defaultValue);
    
    /**
     * Get parameter value as long
     * @param key parameter key
     * @return parameter value as long
     */
    public long getLong(String key);
    
    /**
     * Get parameter value as long with default
     * @param key parameter key
     * @param defaultValue default value if key not found
     * @return parameter value as long or default value
     */
    public long getLong(String key, long defaultValue);
    
    /**
     * Get parameter value as double
     * @param key parameter key
     * @return parameter value as double
     */
    public double getDouble(String key);
    
    /**
     * Get parameter value as double with default
     * @param key parameter key
     * @param defaultValue default value if key not found
     * @return parameter value as double or default value
     */
    public double getDouble(String key, double defaultValue);
    
    /**
     * Get parameter value as boolean
     * @param key parameter key
     * @return parameter value as boolean
     */
    public boolean getBoolean(String key);
    
    /**
     * Get parameter value as boolean with default
     * @param key parameter key
     * @param defaultValue default value if key not found
     * @return parameter value as boolean or default value
     */
    public boolean getBoolean(String key, boolean defaultValue);
    
    /**
     * Check if parameter key exists
     * @param key parameter key
     * @return true if key exists, false otherwise
     */
    public boolean has(String key);
    
    /**
     * Convert to Flink Configuration object
     * @return Configuration object with all parameters
     */
    public Configuration getConfiguration();
    
    /**
     * Convert to Properties object
     * @return Properties object with all parameters
     */
    public Properties getProperties();
}

public static void main(String[] args) throws Exception {
    // Parse command line arguments
    ParameterTool params = ParameterTool.fromArgs(args);
    
    // Get parameters with defaults
    String inputPath = params.get("input", "/default/input/path");
    String outputPath = params.get("output", "/default/output/path");
    int parallelism = params.getInt("parallelism", 1);
    boolean verbose = params.getBoolean("verbose", false);
    
    ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
    
    // Use configuration from parameters
    env.getConfig().setGlobalJobParameters(params);
    env.setParallelism(parallelism);
    
    // Create program using parameters
    DataSet<String> input = env.readTextFile(inputPath);
    // ... process data ...
    result.writeAsText(outputPath);
    
    env.execute("Parameterized Job");
}

// Usage from properties file
ParameterTool fileParams = ParameterTool.fromPropertiesFile("/path/to/config.properties");
String dbHost = fileParams.get("database.host", "localhost");
int dbPort = fileParams.getInt("database.port", 5432);

// Combine multiple parameter sources
ParameterTool systemParams = ParameterTool.fromSystemProperties();
ParameterTool combinedParams = fileParams.mergeWith(systemParams);

/**
 * Parameter tool supporting multiple values for the same key
 */
public class MultipleParameterTool implements Serializable {
    
    /**
     * Create from command line arguments allowing multiple values
     * @param args command line arguments
     * @return MultipleParameterTool instance
     */
    public static MultipleParameterTool fromArgs(String[] args);
    
    /**
     * Get all values for a key
     * @param key parameter key
     * @return list of all values for the key
     */
    public List<String> getMultiple(String key);
    
    /**
     * Get first value for a key
     * @param key parameter key
     * @return first value or null if not found
     */
    public String get(String key);
    
    /**
     * Convert to regular ParameterTool (keeps only first value per key)
     * @return ParameterTool instance
     */
    public ParameterTool getParameterTool();
}

/**
 * Utility class for DataSet operations
 */
public class DataSetUtils {
    
    /**
     * Zip DataSet elements with sequential index
     * @param input input DataSet
     * @return DataSet of Tuple2 with index and original element
     */
    public static <T> DataSet<Tuple2<Long, T>> zipWithIndex(DataSet<T> input);
    
    /**
     * Zip DataSet elements with unique ID
     * @param input input DataSet
     * @return DataSet of Tuple2 with unique ID and original element
     */
    public static <T> DataSet<Tuple2<Long, T>> zipWithUniqueId(DataSet<T> input);
    
    /**
     * Sample elements from DataSet
     * @param input input DataSet
     * @param withReplacement whether to sample with replacement
     * @param fraction fraction of elements to sample (0.0 to 1.0)
     * @return DataSet with sampled elements
     */
    public static <T> DataSet<T> sample(DataSet<T> input, boolean withReplacement, double fraction);
    
    /**
     * Sample elements from DataSet with random seed
     * @param input input DataSet
     * @param withReplacement whether to sample with replacement
     * @param fraction fraction of elements to sample
     * @param seed random seed for reproducible sampling
     * @return DataSet with sampled elements
     */
    public static <T> DataSet<T> sample(DataSet<T> input, boolean withReplacement, double fraction, long seed);
    
    /**
     * Sample fixed number of elements from DataSet
     * @param input input DataSet
     * @param withReplacement whether to sample with replacement
     * @param numSamples number of samples to take
     * @return DataSet with sampled elements
     */
    public static <T> DataSet<T> sampleWithSize(DataSet<T> input, boolean withReplacement, int numSamples);
    
    /**
     * Sample fixed number of elements with random seed
     * @param input input DataSet
     * @param withReplacement whether to sample with replacement
     * @param numSamples number of samples to take
     * @param seed random seed for reproducible sampling
     * @return DataSet with sampled elements
     */
    public static <T> DataSet<T> sampleWithSize(DataSet<T> input, boolean withReplacement, int numSamples, long seed);
    
    /**
     * Count elements in each partition
     * @param input input DataSet
     * @return DataSet with partition ID and element count pairs
     */
    public static <T> DataSet<Tuple2<Integer, Long>> countElementsPerPartition(DataSet<T> input);
}

// Add sequential index to elements
DataSet<String> words = env.fromElements("hello", "world", "flink");
DataSet<Tuple2<Long, String>> indexed = DataSetUtils.zipWithIndex(words);
// Result: (0, "hello"), (1, "world"), (2, "flink")

// Add unique IDs (not necessarily sequential)
DataSet<Tuple2<Long, String>> withIds = DataSetUtils.zipWithUniqueId(words);

// Sample 50% of elements
DataSet<String> largeDatatSet = env.readTextFile("/path/to/large/file.txt");
DataSet<String> sample = DataSetUtils.sample(largeDatatSet, false, 0.5);

// Sample fixed number of elements
DataSet<String> fixedSample = DataSetUtils.sampleWithSize(largeDatatSet, false, 1000);

// Sample with seed for reproducible results
DataSet<String> reproducibleSample = DataSetUtils.sample(largeDatatSet, false, 0.1, 12345L);

// Count elements per partition
DataSet<Tuple2<Integer, Long>> partitionCounts = DataSetUtils.countElementsPerPartition(largeDatatSet);

/**
 * Interface for column summary statistics
 */
public interface ColumnSummary {
    /**
     * Get total count of elements
     * @return total element count
     */
    long getTotalCount();
    
    /**
     * Get count of null elements
     * @return null element count
     */
    long getNullCount();
    
    /**
     * Get count of non-null elements
     * @return non-null element count
     */
    long getNonNullCount();
}

/**
 * Summary statistics for numeric columns
 * @param <T> numeric type (Integer, Long, Double, etc.)
 */
public interface NumericColumnSummary<T> extends ColumnSummary {
    /**
     * Get minimum value
     * @return minimum value
     */
    T getMin();
    
    /**
     * Get maximum value
     * @return maximum value
     */
    T getMax();
    
    /**
     * Get sum of all values
     * @return sum
     */
    Double getSum();
    
    /**
     * Get mean (average) value
     * @return mean value
     */
    Double getMean();
    
    /**
     * Get variance
     * @return variance
     */
    Double getVariance();
    
    /**
     * Get standard deviation
     * @return standard deviation
     */
    Double getStandardDeviation();
}

/**
 * Summary statistics for string columns
 */
public interface StringColumnSummary extends ColumnSummary {
    /**
     * Get minimum string length
     * @return minimum length
     */
    Integer getMinLength();
    
    /**
     * Get maximum string length
     * @return maximum length
     */
    Integer getMaxLength();
    
    /**
     * Get mean string length
     * @return mean length
     */
    Double getMeanLength();
    
    /**
     * Check if all values are numeric
     * @return true if all non-null values are numeric
     */
    Boolean getIsNumeric();
}

/**
 * Summary statistics for boolean columns
 */
public interface BooleanColumnSummary extends ColumnSummary {
    /**
     * Get count of true values
     * @return true count
     */
    Long getTrueCount();
    
    /**
     * Get count of false values
     * @return false count
     */
    Long getFalseCount();
}

/**
 * Container class for function annotations
 */
public class FunctionAnnotation {
    
    /**
     * Annotation to specify forwarded fields
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface ForwardedFields {
        String[] value();
    }
    
    /**
     * Annotation for forwarded fields from first input (for two-input functions)
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface ForwardedFieldsFirst {
        String[] value();
    }
    
    /**
     * Annotation for forwarded fields from second input (for two-input functions)
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface ForwardedFieldsSecond {
        String[] value();
    }
    
    /**
     * Annotation to specify non-forwarded fields
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface NonForwardedFields {
        String[] value();
    }
    
    /**
     * Annotation to specify which fields are read by the function
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface ReadFields {
        String[] value();
    }
    
    /**
     * Annotation to specify which fields are not read by the function
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface SkippedFields {
        String[] value();
    }
}

// Function that forwards first field unchanged
@FunctionAnnotation.ForwardedFields("0")
public static class AddConstantMap implements MapFunction<Tuple2<String, Integer>, Tuple2<String, Integer>> {
    @Override
    public Tuple2<String, Integer> map(Tuple2<String, Integer> value) {
        return new Tuple2<>(value.f0, value.f1 + 10); // field 0 is forwarded, field 1 is modified
    }
}

// Join function that forwards fields from both inputs
@FunctionAnnotation.ForwardedFieldsFirst("0")
@FunctionAnnotation.ForwardedFieldsSecond("1")
public static class CombineJoin implements JoinFunction<Tuple2<String, Integer>, Tuple2<String, Double>, Tuple3<String, Integer, Double>> {
    @Override
    public Tuple3<String, Integer, Double> join(Tuple2<String, Integer> first, Tuple2<String, Double> second) {
        return new Tuple3<>(first.f0, first.f1, second.f1);
    }
}

// Function that only reads certain fields
@FunctionAnnotation.ReadFields("1;2") // only reads fields 1 and 2
public static class PartialReader implements MapFunction<Tuple4<String, Integer, Double, Boolean>, String> {
    @Override
    public String map(Tuple4<String, Integer, Double, Boolean> value) {
        return "Value: " + value.f1 + ", " + value.f2; // only uses f1 and f2
    }
}

import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.api.java.utils.MultipleParameterTool;
import org.apache.flink.api.java.utils.DataSetUtils;
import org.apache.flink.api.java.summarize.*;
import org.apache.flink.api.java.functions.FunctionAnnotation;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.api.java.tuple.Tuple2;
import java.util.Properties;
import java.util.List;
import java.util.Map;
import java.io.IOException;