Merge pull request eugenp#4029 from theawesomenayak/BAEL-1675

[BAEL-1675] Write to a File in Kotlin

Author: CalamarBicefalo

core-kotlin/src/main/kotlin/com/baeldung/filesystem/FileWriter.kt

@@ -0,0 +1,19 @@
+package com.baeldung.filesystem
+
+import java.io.File
+
+class FileWriter {
+
+    fun writeFileUsingPrintWriter(fileName: String, fileContent: String) =
+            File(fileName).printWriter().use { out -> out.print(fileContent) }
+
+    fun writeFileUsingBufferedWriter(fileName: String, fileContent: String) =
+            File(fileName).bufferedWriter().use { out -> out.write(fileContent) }
+
+    fun writeFileDirectly(fileName: String, fileContent: String) =
+            File(fileName).writeText(fileContent)
+
+    fun writeFileDirectlyAsBytes(fileName: String, fileContent: String) =
+            File(fileName).writeBytes(fileContent.toByteArray())
+
+}

core-kotlin/src/test/kotlin/com/baeldung/filesystem/FileWriterTest.kt

@@ -0,0 +1,43 @@
+package com.baeldung.filesystem
+
+import org.junit.jupiter.api.Test
+import java.io.File
+import kotlin.test.assertEquals
+
+internal class FileWriterTest {
+
+    private val fileName = "src/test/resources/Kotlin.out"
+
+    private val fileContent = "Kotlin\nConcise, Safe, Interoperable, Tool-friendly"
+
+    private val fileWriter = FileWriter()
+
+    @Test
+    fun whenWrittenWithPrintWriter_thenCorrect() {
+        fileWriter.writeFileUsingPrintWriter(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
+    }
+
+    @Test
+    fun whenWrittenWithBufferedWriter_thenCorrect() {
+        fileWriter.writeFileUsingBufferedWriter(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
+    }
+
+    @Test
+    fun whenWrittenDirectly_thenCorrect() {
+        fileWriter.writeFileDirectly(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
+    }
+
+    @Test
+    fun whenWrittenDirectlyAsBytes_thenCorrect() {
+        fileWriter.writeFileDirectlyAsBytes(fileName, fileContent)
+
+        assertEquals(fileContent, File(fileName).readText())
+    }
+
+}