[SCALA-26] review refactoring

Author: artem.kupchinskiy

core-scala/src/main/scala/com/baeldung/scala/equality/package.scala

@@ -0,0 +1,17 @@
+package com.baeldung.scala
+
+package object equality {
+  class PersonSimpleClass(val name: String, val age: Int)
+
+  class PersonClassWithOverrides(val name: String, val age: Int) {
+    override def equals(other: Any): Boolean = other match {
+      case person: PersonClassWithOverrides =>
+        this.name == person.name && this.age == person.age
+      case _ => false
+    }
+
+    override def hashCode(): Int = if (name eq null) age else name.hashCode + 31 * age
+  }
+
+  case class PersonCaseClass(name: String, age: Int)
+}

core-scala/src/test/scala/com/baeldung/scala/equality/EqualityTest.scala

@@ -0,0 +1,56 @@
+package com.baeldung.scala.equality
+
+import org.scalatest.FlatSpec
+
+class EqualityTest extends FlatSpec {
+  "Equality operator for AnyVal" should "work as in Java" in {
+    val intAnyVal = 4
+    assert(intAnyVal == 2 * 2)
+  }
+
+  "Equality operator for referential types" should "work like null-safe equals()" in {
+    val firstString = new String("AnyRef")
+    val secondString = new String("AnyRef")
+    val thirdString = null
+    val fourthString = null
+    assert(firstString == secondString)
+    // Unlike in java, the following lines of code do not cause NullPointerExceptions
+    assert(thirdString != secondString)
+    assert(fourthString == thirdString)
+  }
+
+  "Equals()" should "work as in Java" in {
+    val firstString = new String("AnyRef")
+    val secondString = new String("AnyRef")
+    assert(firstString.equals(secondString))
+  }
+
+  "Eq and ne" should "check referential equality" in {
+    val firstString = new String("AnyRef")
+    val secondString = new String("AnyRef")
+    val thirdString = secondString
+    assert(firstString ne secondString)
+    assert(thirdString eq secondString)
+    // Both operators are null-safe
+    assert(null eq null)
+    assert(null ne firstString)
+  }
+
+  "Equality operator" should "not work out of the box for PersonSimpleClass" in {
+    val firstSimpleClassInstance = new PersonSimpleClass("Donald", 66)
+    val secondSimpleClassInstance = new PersonSimpleClass("Donald", 66)
+    assert(firstSimpleClassInstance != secondSimpleClassInstance)
+  }
+
+  "Equality operator" should "work for PersonClassWithOverrides" in {
+    val firstClassWithOverridesInstance = new PersonClassWithOverrides("Donald", 66)
+    val secondClassWithOverridesInstance = new PersonClassWithOverrides("Donald", 66)
+    assert(firstClassWithOverridesInstance == secondClassWithOverridesInstance)
+  }
+
+  "Equality operator" should "work for PersonCaseClass" in {
+    val firstCaseClassInstance = PersonCaseClass("Donald", 66)
+    val secondCaseClassInstance = PersonCaseClass("Donald", 66)
+    assert(firstCaseClassInstance == secondCaseClassInstance)
+  }
+}