Merge pull request #5416 from chandra1123/BAEL-2041

Bael-2041 Introduction to Scala

.gitignore

@@ -63,4 +63,6 @@ jmeter/src/main/resources/*-JMeter.csv
 **/tmp
 **/out-tsc
 **/nbproject/
-**/nb-configuration.xml
+**/nb-configuration.xml
+core-scala/.cache-main
+core-scala/.cache-tests

core-scala/pom.xml

@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-scala</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.scala-lang</groupId>
+            <artifactId>scala-library</artifactId>
+            <version>${scala.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <sourceDirectory>src/main/scala</sourceDirectory>
+        <testSourceDirectory>src/test/scala</testSourceDirectory>
+        <plugins>
+            <plugin>
+                <groupId>net.alchim31.maven</groupId>
+                <artifactId>scala-maven-plugin</artifactId>
+                <version>3.3.2</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>compile</goal>
+                            <goal>testCompile</goal>
+                        </goals>
+                        <configuration>
+                            <args>
+                                <arg>-dependencyfile</arg>
+                                <arg>${project.build.directory}/.scala_dependencies</arg>
+                            </args>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <scala.version>2.12.7</scala.version>
+    </properties>
+</project>
+

core-scala/src/main/scala/com/baeldung/scala/ControlStructuresDemo.scala

@@ -0,0 +1,44 @@
+package com.baeldung.scala
+
+/**
+ * Sample code demonstrating the various control structured.
+ *
+ * @author Chandra Prakash
+ *
+ */
+object ControlStructuresDemo {
+  def gcd(x : Int, y : Int) : Int = {
+    if (y == 0) x else gcd(y, x % y)
+  }
+
+  def gcdIter(x : Int, y : Int) : Int = {
+    var a = x
+    var b = y
+    while (b > 0) {
+      a = a % b
+      val t = a
+      a = b
+      b = t
+    }
+    a
+  }
+
+  def rangeSum(a : Int, b : Int) = {
+    var sum = 0;
+    for (i <- a to b) {
+      sum += i
+    }
+    sum
+  }
+
+  def factorial(a : Int) : Int = {
+    var result = 1;
+    var i = 1;
+    do {
+      result *= i
+      i = i + 1
+    } while (i <= a)
+    result
+  }
+
+}

core-scala/src/main/scala/com/baeldung/scala/Employee.scala

@@ -0,0 +1,27 @@
+package com.baeldung.scala
+
+/**
+ * Sample Code demonstrating a class.
+ *
+ * @author Chandra Prakash
+ *
+ */
+class Employee(val name : String,
+               var salary : Int,
+               annualIncrement : Int = 20) {
+
+  def incrementSalary() : Unit = {
+    salary += annualIncrement
+  }
+
+  override def toString =
+    s"Employee(name=$name, salary=$salary)"
+}
+
+/**
+ * A Trait which will make the toString return upper case value.
+ */
+trait UpperCasePrinter {
+  override def toString = super.toString toUpperCase
+}
+

core-scala/src/main/scala/com/baeldung/scala/HelloWorld.scala

@@ -0,0 +1,6 @@
+package com.baeldung.scala
+
+object HelloWorld extends App {
+  println("Hello World!")
+  args foreach println
+}

core-scala/src/main/scala/com/baeldung/scala/HigherOrderFunctions.scala

@@ -0,0 +1,27 @@
+package com.baeldung.scala
+
+/**
+ * Sample higher order functions.
+ *
+ * @author Chandra Prakash
+ *
+ */
+object HigherOrderFunctions {
+
+  def mapReduce(r : (Int, Int) => Int,
+                i : Int,
+                m : Int => Int,
+                a : Int, b : Int) = {
+    def iter(a : Int, result : Int) : Int = {
+      if (a > b) result
+      else iter(a + 1, r(m(a), result))
+    }
+    iter(a, i)
+  }
+
+  def whileLoop(condition : => Boolean)(body : => Unit) : Unit =
+    if (condition) {
+      body
+      whileLoop(condition)(body)
+    }
+}

core-scala/src/main/scala/com/baeldung/scala/IntSet.scala

@@ -0,0 +1,34 @@
+package com.baeldung.scala
+
+/**
+ * An abstract class for set of integers and its implementation.
+ *
+ * @author Chandra Prakash
+ *
+ */
+abstract class IntSet {
+  // add an element to the set
+  def incl(x : Int) : IntSet
+
+  // whether an element belongs to the set
+  def contains(x : Int) : Boolean
+}
+
+class EmptyIntSet extends IntSet {
+
+  def contains(x : Int) : Boolean = false
+
+  def incl(x : Int) =
+    new NonEmptyIntSet(x, this)
+}
+
+class NonEmptyIntSet(val head : Int, val tail : IntSet)
+  extends IntSet {
+
+  def contains(x : Int) : Boolean =
+    head == x || (tail contains x)
+
+  def incl(x : Int) : IntSet =
+    if (this contains x) this
+    else new NonEmptyIntSet(x, this)
+}

core-scala/src/main/scala/com/baeldung/scala/Utils.scala

@@ -0,0 +1,33 @@
+package com.baeldung.scala
+
+/**
+ * Some utility methods.
+ *
+ * @author Chandra Prakash
+ *
+ */
+object Utils {
+  def average(x : Double, y : Double) = (x + y) / 2
+
+  def randomLessThan(d : Double) = {
+    var random = 0d
+    do {
+      random = Math.random()
+    } while (random >= d)
+    random
+  }
+
+  def power(x : Int, y : Int) : Int = {
+    def powNested(i : Int, accumulator : Int) : Int = {
+      if (i <= 0) accumulator
+      else powNested(i - 1, x * accumulator)
+    }
+    powNested(y, 1)
+  }
+
+  def fibonacci(n : Int) : Int = n match {
+    case 0 | 1 => 1
+    case x if x > 1 =>
+      fibonacci(x - 1) + fibonacci(x - 2)
+  }
+}

core-scala/src/test/scala/com/baeldung/scala/ControlStructuresDemoUnitTest.scala

@@ -0,0 +1,33 @@
+package com.baeldung.scala
+
+import com.baeldung.scala.ControlStructuresDemo._
+import org.junit.Test
+import org.junit.Assert.assertEquals
+
+class ControlStructuresDemoUnitTest {
+  @Test
+  def givenTwoIntegers_whenGcdCalled_thenCorrectValueReturned = {
+    assertEquals(3, gcd(15, 27))
+  }
+
+  @Test
+  def givenTwoIntegers_whenGcdIterCalled_thenCorrectValueReturned = {
+    assertEquals(3, gcdIter(15, 27))
+  }
+
+  @Test
+  def givenTwoIntegers_whenRangeSumcalled_thenCorrectValueReturned = {
+    assertEquals(55, rangeSum(1, 10))
+  }
+
+  @Test
+  def givenPositiveInteger_whenFactorialInvoked_thenCorrectValueReturned = {
+    assertEquals(720, factorial(6))
+  }
+
+  @Test
+  def whenFactorialOf0Invoked_then1Returned = {
+    assertEquals(1, factorial(0))
+  }
+
+}

core-scala/src/test/scala/com/baeldung/scala/EmployeeUnitTest.scala

@@ -0,0 +1,30 @@
+package com.baeldung.scala
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class EmployeeUnitTest {
+
+  @Test
+  def whenEmployeeSalaryIncremented_thenCorrectSalary = {
+    val employee = new Employee("John Doe", 1000)
+    employee.incrementSalary()
+    assertEquals(1020, employee.salary)
+  }
+
+  @Test
+  def givenEmployee_whenToStringCalled_thenCorrectStringReturned = {
+    val employee = new Employee("John Doe", 1000)
+    assertEquals("Employee(name=John Doe, salary=1000)", employee.toString)
+  }
+
+  @Test
+  def givenEmployeeWithTrait_whenToStringCalled_thenCorrectStringReturned = {
+    val employee =
+      new Employee("John Doe", 1000) with UpperCasePrinter
+    assertEquals("EMPLOYEE(NAME=JOHN DOE, SALARY=1000)", employee.toString)
+  }
+
+}
+
+

core-scala/src/test/scala/com/baeldung/scala/HigherOrderFunctionsUnitTest.scala

@@ -0,0 +1,49 @@
+package com.baeldung.scala
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+import HigherOrderFunctions.mapReduce
+
+class HigherOrderFunctionsUnitTest {
+
+  @Test
+  def whenCalledWithSumAndSquareFunctions_thenCorrectValueReturned = {
+    def square(x : Int) = x * x
+
+    def sum(x : Int, y : Int) = x + y
+
+    def sumSquares(a : Int, b : Int) =
+      mapReduce(sum, 0, square, a, b)
+
+    assertEquals(385, sumSquares(1, 10))
+  }
+
+  @Test
+  def whenComputingSumOfSquaresWithAnonymousFunctions_thenCorrectValueReturned = {
+    def sumSquares(a : Int, b : Int) =
+      mapReduce((x, y) => x + y, 0, x => x * x, a, b)
+
+    assertEquals(385, sumSquares(1, 10))
+  }
+
+  @Test
+  def givenCurriedFunctions_whenInvoked_thenCorrectValueReturned = {
+    // a curried function
+    def sum(f : Int => Int)(a : Int,
+                            b : Int) : Int =
+      if (a > b) 0 else f(a) + sum(f)(a + 1, b)
+
+    // another curried function
+    def mod(n : Int)(x : Int) = x % n
+
+    // application of a curried function
+    assertEquals(1, mod(5)(6))
+
+    // partial application of curried function
+    // trailing underscore is required to make function type explicit
+    val sumMod5 = sum(mod(5)) _
+
+    assertEquals(10, sumMod5(6, 10))
+  }
+}

core-scala/src/test/scala/com/baeldung/scala/IntSetUnitTest.scala

@@ -0,0 +1,23 @@
+package com.baeldung.scala
+
+import scala.Range
+
+import org.junit.Assert.assertFalse
+import org.junit.Test
+
+class IntSetUnitTest {
+
+  @Test
+  def givenSetof1To10_whenContains11Called_thenFalse = {
+
+    // Set up a set containing integers 1 to 10.
+    val set1To10 =
+      Range(1, 10)
+        .foldLeft(new EmptyIntSet() : IntSet) {
+          (x, y) => x incl y
+        }
+
+    assertFalse(set1To10 contains 11)
+  }
+
+}

core-scala/src/test/scala/com/baeldung/scala/UtilsUnitTest.scala

@@ -0,0 +1,37 @@
+package com.baeldung.scala
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+import Utils.average
+import Utils.fibonacci
+import Utils.power
+import Utils.randomLessThan
+
+class UtilsUnitTest {
+
+  @Test
+  def whenAverageCalled_thenCorrectValueReturned() = {
+    assertEquals(15.0, average(10, 20), 1e-5)
+  }
+
+  @Test
+  def whenRandomLessThanInvokedWithANumber_thenARandomLessThanItReturned = {
+    val d = 0.1
+    assertTrue(randomLessThan(d) < d)
+  }
+
+  @Test
+  def whenPowerInvokedWith2And3_then8Returned = {
+    assertEquals(8, power(2, 3))
+  }
+
+  @Test
+  def whenFibonacciCalled_thenCorrectValueReturned = {
+    assertEquals(1, fibonacci(0))
+    assertEquals(1, fibonacci(1))
+    assertEquals(fibonacci(6),
+      fibonacci(4) + fibonacci(5))
+  }
+}

pom.xml

@@ -386,6 +386,7 @@
 				<module>guava-modules/guava-21</module>
 				<module>guice</module>
 				<module>disruptor</module>
+				<module>core-scala</module>
 				<module>spring-static-resources</module>
 				<module>hazelcast</module>
 				<module>persistence-modules/hbase</module>