[Java] File, ByteArray, String, Stream Conversion Examples

1. ByteArray To File

1) JDK ByteArray To Path

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static void byteArrayToFileName(byte[] data, String file) throws IOException { java.nio.file.Files.write(Paths.get(file), data); }

2) Commons(FileUtils) ByteArray To File

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static void byteArrayToFile(byte[] data, File file ) throws IOException { org.apache.commons.io.FileUtils.writeByteArrayToFile(file, data); }

3) Guava ByteArray To File

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static void guavaByteArrayToFile(byte[] data, File file ) throws IOException { com.google.common.io.Files.write(data, file); }

2. File To ByteArray

1) JDK Path to ByteArray

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static byte[] fileNameToByteArray(String file ) throws IOException { return java.nio.file.Files.readAllBytes(Paths.get(file)); }

2) Commons(FileUtils) File To ByteArray

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static byte[] fileToByteArray( File file ) throws IOException { return org.apache.commons.io.FileUtils.readFileToByteArray(file); }

3. InputStream to ByteArray

1) Commons(IOUtils) InputStream To ByteArray

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static byte[] inputStreamToByteArray( InputStream is ) throws IOException { return org.apache.commons.io.IOUtils.toByteArray(is); }

2) Guava InputStream To ByteArray

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static byte[] guavaInputStreamToByteArray( InputStream is ) throws IOException { return ByteStreams.toByteArray(is); }

3) JDK InputStream To ByteArray using ByteArrayOutputStream

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static byte[] inputStreamToByteStream( InputStream is ) throws IOException { ByteArrayOutputStream buffer = new ByteArrayOutputStream(); byte[] data = new byte[16384]; int len; while ((len = is.read(data)) >= 0 ) { buffer.write(data, 0, len); } buffer.flush(); return buffer.toByteArray(); }

4. ByteArray to InputStream

1) JDK ByteArray To InputStream

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static InputStream byteArrayToInputStream(byte[] data) { return new ByteArrayInputStream(data); }

5. File To LinesArray

1) File To LinesArray using Scanner

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static String[] readFileLines(File file) throws FileNotFoundException { List<String> lines = new ArrayList<>(); final Scanner s = new Scanner(file); while(s.hasNextLine()) { lines.add(s.nextLine()); } return lines.toArray(new String[lines.size()]); }

2) File To LinesArray using BufferedReader

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static String[] fileToLinesArray(File file) throws FileNotFoundException, IOException { List<String> lines = new ArrayList<>(); BufferedReader br = new BufferedReader(new FileReader(file)); while(true) { String line = br.readLine(); if( line == null ) { break; } lines.add(line); } br.close(); return lines.toArray(new String[lines.size()]); }

6. List To Array

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static void listToArray() { List<Integer> list = new ArrayList<>(); list.add(1); list.add(2); list.add(3); Integer[] array = list.toArray(new Integer[list.size()]); }

7. Array To List

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static void arrayToList() { Integer[] values = { 1, 2, 3 }; List<Integer> list = new ArrayList<>(Arrays.asList(values)); int[] values2 = new int[] { 1, 2, 3 }; list = Arrays.stream(values2).boxed().collect(Collectors.toList()); list = Arrays.stream(values2).boxed().collect(Collectors.toCollection(ArrayList::new)); list = Arrays.stream(values2).boxed().collect(Collectors.toCollection(LinkedList::new)); }