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Interface	Common Implementation(s)	Comparison Method
Set	HashSet	hashCode → equals
Map	HashMap	hashCode → equals (for keys)
List	ArrayList, LinkedList	equals only (sequential)
SortedSet	TreeSet	compareTo / Comparator
SortedMap	TreeMap	compareTo / Comparator
LinkedHashSet	Linked hash table (ordered)	hashCode → equals
LinkedHashMap	Linked hash table (ordered)	hashCode → equals

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public class Person {
    private final String firstName;
    private final String lastName;

    public Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName  = lastName;
    }

    @Override

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class Person(val firstName: String, val lastName: String) {

    override fun equals(other: Any?): Boolean {
        val otherPerson = other as? Person ?: return false
        return otherPerson.firstName == firstName &&
               otherPerson.lastName == lastName
    }

    override fun hashCode(): Int =
        firstName.hashCode() * 31 + lastName.hashCode()

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override fun hashCode(): Int = firstName.hashCode() * 37 + lastName.hashCode()

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override fun equals(other: Any?): Boolean {
    val otherPerson = other as? Person ?: return false
    return otherPerson.firstName == firstName &&
           otherPerson.lastName == lastName
}

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class Person(val firstName: String, val lastName: String) {
    override fun equals(other: Any?): Boolean {
        val otherPerson = other as? Person ?: return false
        return otherPerson.firstName == firstName &&
            otherPerson.lastName == lastName
    }

    override fun hashCode(): Int = firstName.hashCode() * 37 + lastName.hashCode()
}

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val program =
  for {
    _ <- Console.printLine("Starting…")
    _ <- Console.printLine("Doing work…")
    _ <- Console.printLine("Finished!")
  } yield ()

Runtime.default.unsafeRun(program) // single execution point

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// (1) Pure computation stage
fun calculateSomething(input: Int): Int =
    input * 2 + 1

// (2) Stage that *describes* an effect
data class WriteToFileCommand(val path: String, val content: String)

// (3) Stage that *performs* the effect
fun executeCommand(cmd: WriteToFileCommand) {
    File(cmd.path).writeText(cmd.content)

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import kafka.utils.ZkUtils

object KafkaTopicTest {
  def createZkUtils(): ZkUtils = {
    val zookeepers = "localhost:2181"
    val timeout = 10000
    ZkUtils(zookeepers, timeout, timeout, isZkSecurityEnabled = false)
  }

  def getPartitionsForTopics(topics: Seq[String]): Map[String, Seq[Int]] = {

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#!/bin/bash

kafka_home=$1
zookeeper=$2
group_name=$3
lag_threshold=$4
lag_data_sampling_count=$5
if [ ! -z $6 ] ; then
	lag_data_file=$6
else