Exercise: Make DeckConnector comparable
Change the DeckConnector class:
- Implement a
compareTomethod so it first compares values based on thedeckNameproperty; if they are equal, then compare them based on thestateproperty ordinal. - Implement
equalsandhashCodemethods so that twoDeckConnectorinstances are equal if theirdeckNameandstateproperties are equal.
class DeckConnector(
val deckName: String
) : Comparable<DeckConnector> {
var state: ConnectionState = ConnectionState.Initial
override fun compareTo(other: DeckConnector): Int {
TODO("Not yet implemented")
}
enum class ConnectionState {
Initial,
Connected,
Disconnected
}
}
This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in effective/design/DeckConnector.kt. You can find there starting code and unit tests.
Once you are done with the exercise, you can check your solution here.
Playground
import org.junit.Test
import java.util.*
import kotlin.test.assertEquals
import kotlin.test.assertNotEquals
class DeckConnector(
val deckName: String
) : Comparable<DeckConnector> {
var state: ConnectionState = ConnectionState.Initial
override fun compareTo(other: DeckConnector): Int {
TODO("Not yet implemented")
}
enum class ConnectionState {
Initial,
Connected,
Disconnected
}
}
class DeckConnectorTest {
@Test
fun `should be equal when deck name and state are equal`() {
val deckConnector1 = DeckConnector("deck1")
val deckConnector2 = DeckConnector("deck1")
assertEquals(deckConnector1, deckConnector2)
}
@Test
fun `should not equal when deck name or state are different`() {
val deckConnector1 = DeckConnector("deck1")
val deckConnector2 = DeckConnector("deck1")
val deckConnector3 = DeckConnector("deck2")
assertNotEquals(deckConnector1, deckConnector3)
assertEquals(deckConnector1, deckConnector2)
deckConnector1.state = DeckConnector.ConnectionState.Connected
assertNotEquals(deckConnector1, deckConnector2)
deckConnector2.state = DeckConnector.ConnectionState.Connected
assertEquals(deckConnector1, deckConnector2)
}
@Test
fun `should have equal hash code for equal objects`() {
val deckConnector1 = DeckConnector("deck1")
val deckConnector2 = DeckConnector("deck1")
val deckConnector3 = DeckConnector("deck2")
assertNotEquals(deckConnector1.hashCode(), deckConnector3.hashCode())
assertEquals(deckConnector1.hashCode(), deckConnector2.hashCode())
deckConnector1.state = DeckConnector.ConnectionState.Connected
assertNotEquals(deckConnector1.hashCode(), deckConnector2.hashCode())
deckConnector2.state = DeckConnector.ConnectionState.Connected
assertEquals(deckConnector1.hashCode(), deckConnector2.hashCode())
}
@Test
fun `should compare objects by deck name and state`() {
val deck1 = DeckConnector("deck1").apply { state = DeckConnector.ConnectionState.Connected }
val deck2 = DeckConnector("deck2").apply { state = DeckConnector.ConnectionState.Connected }
val deck3 = DeckConnector("deck2").apply { state = DeckConnector.ConnectionState.Disconnected }
val sortedDecks = listOf(
deck1,
DeckConnector("deck1").apply { state = DeckConnector.ConnectionState.Disconnected },
deck2,
deck3,
DeckConnector("deck3").apply { state = DeckConnector.ConnectionState.Connected },
DeckConnector("deck3").apply { state = DeckConnector.ConnectionState.Disconnected }
)
assertEquals(sortedDecks, sortedDecks.shuffled().sorted())
assert(deck1 < deck2)
assert(deck2 < deck3)
assert(deck1 < deck3)
assert(deck2 > deck1)
assert(deck3 > deck2)
assert(deck3 > deck1)
assert(deck1 <= deck1)
assert(deck2 <= deck2)
assert(deck3 <= deck3)
}
}
