BAEL-6776: Convert File to Byte Array in Java (#15123)

core-java-modules/core-java-io-conversions-2/src/test/java/com/baeldung/filetofrombytearray/FileToByteArrayUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.filetofrombytearray;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.IOUtils;
+import org.junit.jupiter.api.Test;
+
+class FileToByteArrayUnitTest {
+
+    private static final String FILE_NAME = "src" + File.separator + "test" + File.separator + "resources" + File.separator + "sample.txt";
+    private final byte[] expectedByteArray = { 72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100 };
+
+    @Test
+    void givenFile_whenUsingFileInputStreamClass_thenConvert() throws IOException {
+        File myFile = new File(FILE_NAME);
+        byte[] byteArray = new byte[(int) myFile.length()];
+        try (FileInputStream inputStream = new FileInputStream(myFile)) {
+            inputStream.read(byteArray);
+        }
+
+        assertArrayEquals(expectedByteArray, byteArray);
+    }
+
+    @Test
+    void givenFile_whenUsingNioApiFilesClass_thenConvert() throws IOException {
+        byte[] byteArray = Files.readAllBytes(Paths.get(FILE_NAME));
+
+        assertArrayEquals(expectedByteArray, byteArray);
+    }
+
+    @Test
+    void givenFile_whenUsingApacheCommonsIOUtilsClass_thenConvert() throws IOException {
+        File myFile = new File(FILE_NAME);
+        byte[] byteArray = new byte[(int) myFile.length()];
+        try (FileInputStream inputStream = new FileInputStream(myFile)) {
+            byteArray = IOUtils.toByteArray(inputStream);
+        }
+
+        assertArrayEquals(expectedByteArray, byteArray);
+    }
+
+    @Test
+    void givenFile_whenUsingApacheCommonsFileUtilsClass_thenConvert() throws IOException {
+        byte[] byteArray = FileUtils.readFileToByteArray(new File(FILE_NAME));
+
+        assertArrayEquals(expectedByteArray, byteArray);
+    }
+
+    @Test
+    void givenFile_whenUsingGuavaFilesClass_thenConvert() throws IOException {
+        byte[] byteArray = com.google.common.io.Files.toByteArray(new File(FILE_NAME));
+
+        assertArrayEquals(expectedByteArray, byteArray);
+    }
+
+}