InputStream to String in Kotlin BAEL-2654

core-kotlin-2/src/main/kotlin/com/baeldung/inputstream/InputStreamExtension.kt

@@ -0,0 +1,17 @@
+package com.baeldung.inputstream
+
+import java.io.InputStream
+
+fun InputStream.readUpToNullChar(nullChar: Char = '\n'): String {
+    val stringBuilder = StringBuilder()
+    var currentChar = this.read().toChar()
+    while (currentChar != nullChar) {
+        stringBuilder.append(currentChar)
+        currentChar = this.read().toChar()
+        if (this.available() <= 0) {
+            stringBuilder.append(currentChar)
+            break
+        }
+    }
+    return stringBuilder.toString()
+}

core-kotlin-2/src/test/kotlin/com/baeldung/inputstream/InputStreamToStringTest.kt

@@ -0,0 +1,43 @@
+package com.baeldung.range
+
+import com.baeldung.inputstream.readUpToNullChar
+import kotlinx.io.core.use
+import org.junit.Test
+import java.io.BufferedReader
+import java.io.File
+import kotlin.test.assertEquals
+
+class InputStreamToStringTest {
+    private val fileName = "src/test/resources/inputstream2string.txt"
+    private val fileFullContent = "Computer programming can be a hassle\r\n" +
+            "It's like trying to take a defended castle"
+    private val fileContentUpToNullChar = "Computer programming can be a hassle\r\n" +
+            "It"
+
+    @Test
+    fun whenReadFileWithBufferedReader_thenFullFileContentIsReadAsString() {
+        val file = File(fileName)
+        val inputStream = file.inputStream()
+        val content = inputStream.bufferedReader().use(BufferedReader::readText)
+        assertEquals(fileFullContent, content)
+    }
+
+    @Test
+    fun whenReadFileUpToNullChar_thenPartBeforeNullCharIsReadAsString() {
+        val file = File(fileName)
+        val inputStream = file.inputStream()
+        val content = inputStream.use { it.readUpToNullChar('\'') }
+        assertEquals(fileContentUpToNullChar, content)
+    }
+
+    @Test
+    fun whenReadFileWithoutContainingNullChar_thenFullFileContentIsReadAsString() {
+        val file = File(fileName)
+        val inputStream = file.inputStream()
+        val content = inputStream.use { it.readUpToNullChar('-') }
+        assertEquals(fileFullContent, content)
+    }
+
+
+}
+

core-kotlin-2/src/test/resources/inputstream2string.txt

@@ -0,0 +1,2 @@
+Computer programming can be a hassle
+It's like trying to take a defended castle