Merge pull request #49 from barbasa/master

SCALA-18: Exception handling

Author: jzheaux

core-scala/src/main/scala/com/baeldung/scala/exceptionhandling/Calculator.scala

@@ -0,0 +1,17 @@
+package com.baeldung.scala.exceptionhandling
+
+object CalculatorExceptions {
+  class IntOverflowException extends RuntimeException
+  class NegativeNumberException extends RuntimeException
+}
+
+object Calculator {
+  import CalculatorExceptions._
+
+  def sum(a: Int, b: Int): Int = {
+    if (a < 0 || b < 0) throw new NegativeNumberException
+    val result = a + b
+    if (result < 0) throw new IntOverflowException
+    result
+  }
+}

core-scala/src/main/scala/com/baeldung/scala/exceptionhandling/Examples.scala

@@ -0,0 +1,34 @@
+package com.baeldung.scala.exceptionhandling
+
+import scala.util.{Try, Success, Failure}
+import scala.util.control.Exception._
+
+object Examples {
+  import CalculatorExceptions._
+  def tryCatch(a: Int, b: Int): Int = {
+    try {
+      return Calculator.sum(a, b)
+      // println(s"${a} + ${b} = ${result}")
+    } catch {
+      case e: IntOverflowException    => -1
+      case e: NegativeNumberException => -2
+    } finally {
+      // This block will always be invoked
+      println("Calculation done!")
+    }
+  }
+
+  def trySuccessFailure(a: Int, b: Int): Try[Int] = Try {
+    Calculator.sum(a, b)
+  }
+
+  def catchObjects(a: Int, b: Int): Try[Int] = allCatch.withTry {
+    Calculator.sum(a, b)
+  }
+
+  val myCustomCatcher = catching(classOf[NegativeNumberException])
+
+  def customCatchObjects(a: Int, b: Int): Try[Int] = myCustomCatcher.withTry {
+    Calculator.sum(a, b)
+  }
+}

core-scala/src/test/scala/com/baeldung/scala/exceptionhandling/ExamplesUnitTest.scala

@@ -0,0 +1,122 @@
+package com.baeldung.scala.exceptionhandling
+
+import org.scalatest._
+import org.scalatest.Assertions._
+import scala.util.{Success, Failure}
+
+class ExamplesUnitTest extends FlatSpec with Matchers {
+
+  "tryCatch" should "handle NegativeNumberException" in {
+    noException should be thrownBy Examples.tryCatch(-1, -2)
+    assert(Examples.tryCatch(-20, -30) == -2)
+  }
+
+  it should "handle IntOverflowException" in {
+    noException should be thrownBy Examples.tryCatch(Int.MaxValue, 1)
+    assert(Examples.tryCatch(Int.MaxValue, 1) == -1)
+  }
+
+  it should "return the correct sum" in {
+    noException should be thrownBy Examples.tryCatch(2, 1)
+    assert(Examples.tryCatch(2, 3) == 5)
+  }
+
+  "trySuccessFailure" should "handle NegativeNumberException" in {
+    import CalculatorExceptions._
+    val result = Examples.trySuccessFailure(-1, -2)
+    result match {
+      case Failure(e) => assert(e.isInstanceOf[NegativeNumberException])
+      case Success(_) => fail("Should fail!")
+    }
+  }
+
+  it should "handle IntOverflowException" in {
+    import CalculatorExceptions._
+    val result = Examples.trySuccessFailure(Int.MaxValue, 1)
+    result match {
+      case Failure(e) => assert(e.isInstanceOf[IntOverflowException])
+      case Success(_) => fail("Should fail!")
+    }
+  }
+
+  it should "return the correct sum" in {
+    import CalculatorExceptions._
+    val result = Examples.trySuccessFailure(3, 2)
+    result match {
+      case Failure(e)      => fail("Should succed!")
+      case Success(result) => assert(result == 5)
+    }
+  }
+
+  "catchObjects" should "handle NegativeNumberException" in {
+    import CalculatorExceptions._
+    val result = Examples.catchObjects(-1, -2)
+    result match {
+      case Failure(e) => assert(e.isInstanceOf[NegativeNumberException])
+      case Success(_) => fail("Should fail!")
+    }
+  }
+
+  it should "handle IntOverflowException" in {
+    import CalculatorExceptions._
+    val result = Examples.catchObjects(Int.MaxValue, 1)
+    result match {
+      case Failure(e) => assert(e.isInstanceOf[IntOverflowException])
+      case Success(_) => fail("Should fail!")
+    }
+  }
+
+  it should "return the correct sum" in {
+    import CalculatorExceptions._
+    val result = Examples.catchObjects(3, 2)
+    result match {
+      case Failure(e)      => fail("Should succed!")
+      case Success(result) => assert(result == 5)
+    }
+  }
+
+  "customCatchObjects" should "handle NegativeNumberException" in {
+    import CalculatorExceptions._
+    val result = Examples.customCatchObjects(-1, -2)
+    result match {
+      case Failure(e) => assert(e.isInstanceOf[NegativeNumberException])
+      case Success(_) => fail("Should fail!")
+    }
+  }
+
+  it should "handle IntOverflowException" in {
+    import CalculatorExceptions._
+    assertThrows[IntOverflowException] {
+      Examples.customCatchObjects(Int.MaxValue, 1)
+    }
+  }
+
+  it should "return the correct sum" in {
+    import CalculatorExceptions._
+    val result = Examples.customCatchObjects(3, 2)
+    result match {
+      case Failure(e)      => fail("Should succed!")
+      case Success(result) => assert(result == 5)
+    }
+  }
+
+  "customCatchObjects composed with trySuccessFailure" should "return the correct sum" in {
+    import CalculatorExceptions._
+    val result = Examples.customCatchObjects(3, 2) flatMap (Examples
+      .trySuccessFailure(_, 3))
+    result match {
+      case Failure(e)      => fail("Should succed!")
+      case Success(result) => assert(result == 8)
+    }
+  }
+
+  it should "print an error" in {
+    import CalculatorExceptions._
+    val result = Examples.customCatchObjects(-1, -2) flatMap (Examples
+      .trySuccessFailure(_, 3))
+    result match {
+      case Failure(e)      => assert(e.isInstanceOf[NegativeNumberException])
+      case Success(result) => fail("Should fail!")
+    }
+  }
+}