Java Utililty Methods File Read via ByteBuffer

List of utility methods to do File Read via ByteBuffer

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Description

The list of methods to do File Read via ByteBuffer are organized into topic(s).

Method

ByteBuffergetReadBuffer(File file)
get Read Buffer 
try (RandomAccessFile f = new RandomAccessFile(file, "r")) {
    return f.getChannel().map(MapMode.READ_ONLY, 0, file.length());
} catch (IOException e) {
    return null;
StringgetStringContents(ReadableByteChannel channel)
Gets String contents from channel and closes it. 
try {
    ByteBuffer buffer = ByteBuffer.allocate(1024 * 8);
    StringBuilder sb = new StringBuilder();
    int bytesRead = channel.read(buffer);
    while (bytesRead != -1) {
        buffer.flip();
        CharBuffer charBuffer = StandardCharsets.UTF_8.decode(buffer);
        sb.append(charBuffer.toString());
...
byte[]largeFileReader(String filename)
good for Large Files >2Mb 
byte[] bytes = null;
FileChannel fc = null;
try {
    fc = new FileInputStream(filename).getChannel();
    MappedByteBuffer byteBuffer = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
    int size = byteBuffer.capacity();
    if (size > 0) {
        byteBuffer.clear();
...
ByteBuffermapReadWrite(File file)
This is a convenience method for mapping an entire File into a ByteBuffer . 
return mapReadWrite(file, 0, file.length());
voidnioCopy(ReadableByteChannel input, WritableByteChannel output)
nio Copy 
try {
    ByteBuffer buffer = ByteBuffer.allocate(DEFAULT_BUFFER_SIZE);
    while (input.read(buffer) != -1) {
        buffer.flip();
        output.write(buffer);
        buffer.compact();
    buffer.flip();
...
MappedByteBufferopenReadOnly(Path path, int offset, int length)
Maps a portion of a file to memory and returns the mapped read-only byte buffer using the given offset and length. 
try (FileChannel fc = FileChannel.open(path, READ)) {
    return fc.map(READ_ONLY, offset, truncateLength(fc, length));
ByteBufferread(DataInput in, int length)
read 
if (length == 0)
    return EMPTY_BYTE_BUFFER;
byte[] buff = new byte[length];
in.readFully(buff);
return ByteBuffer.wrap(buff);
Stringread(File file)
read 
return _collect(file.toPath(), _UTF_8);
Stringread(File file)
read 
return new String(readBytes(file), UTF8);
ByteBufferread(File file, long offset, int length)
read 
FileChannel chan = channel(file, false);
ByteBuffer buf = ByteBuffer.allocate(length);
chan.position(offset);
while (buf.remaining() > 0) {
    if (chan.read(buf) <= 0) {
        throw new IOException("Failed to read from channel.");
buf.rewind();
chan.close();
return buf;