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import jakarta.validation.constraints.NotNull;

@NotNull
public Cart getCart(@NotNull List<Item> items) {
  return CartFactory.createCart(database.getItems(getUser()));
}
  

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package org.mrbear.kotlin.interfaces

interface Person {
    fun getName(): String
    fun getAge(): Int
    fun getGender(): String = "Male"
}

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public class MrBear implements Person {
  @Override
  @NotNull
  public String getName() {
    return "Mr. Bear";
  }

  @Override
  public int getAge() {
    return 50;

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package org.mrbear.kotlin.companionobject

import org.testng.annotations.Test
import java.time.LocalDate
import java.time.Month
import org.assertj.core.api.Assertions.assertThat

class CompanionObjectTest {

    @Test

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package org.mrbear.kotlin.operators

import org.assertj.core.api.Assertions.assertThat
import org.mrbear.kotlin.AddressFactory
import org.mrbear.kotlin.Person
import org.mrbear.kotlin.PersonFactory
import org.testng.annotations.Test

class OperatorOverloadingTest {

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    @Test
    fun testEmpty() {
        val emptyList: List<String> = listOf()

        val anotherEmptyList: List<String> = emptyList()

        assertThat(emptyList).isEmpty()
        assertThat(anotherEmptyList).isEmpty()
        assertThat(emptyList).isEqualTo(anotherEmptyList);
        assertThat(emptyList).isSameAs(anotherEmptyList);

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public class EqualsTest {

  public enum Day {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY}

  /**
   * Sets in Java are un-ordered. Two sets are equal if they contain the same elements.
   */
  @Test
  public void testEqualsSet() {

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enum class ImageMimeType(val description: String) : LookupValue {
    GIF(".git"),
    JPEG(".jpeg"),
    PNG(".png");

    override fun getValue(): String =
        this.name

    override fun getDescription(): String = description

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public interface LookupValue {
  String getValue();

  String getDescription();
}

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@Test
  public void testSortUnsortedStream() {
    Person kenThompson = new Person("Ken", "Thompson");
    Person edgerDijkstra = new Person("Edger", "Dijkstra");
    Person simonThompson = new Person("Simon", "Thompson");
    Set<Person> people = Set.of(
        edgerDijkstra,
        kenThompson,
        simonThompson
    );