BAEL-4721 (#10272)

* BAEL-4721 Examples

* BAEL-4721 Requested edits

* Fix formatting issues

* Correct unit test name

core-java-modules/core-java-io-3/src/test/java/com/baeldung/writebytearray/WriteByteArrayUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.writebytearray;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+
+import org.apache.commons.io.FileUtils;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import com.google.common.io.ByteSink;
+import com.google.common.io.MoreFiles;
+
+public class WriteByteArrayUnitTest {
+    private static byte[] dataForWriting;
+
+    @Rule
+    public TemporaryFolder tempFolder = new TemporaryFolder();
+
+    @BeforeClass
+    public static void setup() throws IOException {
+        dataForWriting = Files.readAllBytes(Paths.get("src/test/resources/example-image.jpg"));
+    }
+
+    @Test
+    public void whenUsingFileOutputStream_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-fos.jpg");
+        try (FileOutputStream outputStream = new FileOutputStream(outputFile)) {
+            outputStream.write(dataForWriting);
+            assertThat(outputFile).hasBinaryContent(dataForWriting);
+        }
+    }
+
+    @Test
+    public void whenUsingNioFiles_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-nio-files.jpg");
+        Files.write(outputFile.toPath(), dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingGuavaFiles_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-guava-files.jpg");
+        com.google.common.io.Files.write(dataForWriting, outputFile);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingGuavaByteSink_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-guava-bs.jpg");
+        ByteSink byteSink = com.google.common.io.Files.asByteSink(outputFile);
+        byteSink.write(dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingGuavaByteSinkMoreFiles_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-guava-bs.jpg");
+        ByteSink byteSink = MoreFiles.asByteSink(outputFile.toPath(), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
+        byteSink.write(dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingCommonsIo_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-file-utils.jpg");
+        FileUtils.writeByteArrayToFile(outputFile, dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+}