File file = new File("DemoRandomAccessFile.out");
RandomAccessFile raf = new RandomAccessFile(file, "r");// Seek to the end of file
raf.seek(file.length() - n);
// Read it out.
raf.read(yourbyteArray, 0, n);

Below are two functions, one that returns the last non-blank line of a file without loading or stepping through the entire file, and the other that returns the last N lines of the file without stepping through the entire file:

What tail does is zoom straight to the last character of the file, then steps backward, character by character, recording what it sees until it finds a line break. Once it finds a line break, it breaks out of the loop. Reverses what was recorded and throws it into a string and returns. 0xA is the new line and 0xD is the carriage return.

public String tail( File file ) {RandomAccessFile fileHandler = null;try {fileHandler = new RandomAccessFile( file, "r" );long fileLength = fileHandler.length() - 1;StringBuilder sb = new StringBuilder();for(long filePointer = fileLength; filePointer != -1; filePointer--){fileHandler.seek( filePointer );int readByte = fileHandler.readByte();if( readByte == 0xA ) {if( filePointer == fileLength ) {continue;} else {break;}} else if( readByte == 0xD ) {if( filePointer == fileLength - 1 ) {continue;} else {break;}}sb.append( ( char ) readByte );}String lastLine = sb.reverse().toString();return lastLine;} catch( java.io.FileNotFoundException e ) {e.printStackTrace();return null;} catch( java.io.IOException e ) {e.printStackTrace();return null;} finally {if (fileHandler != null )try {fileHandler.close();} catch (IOException e) {/* ignore */}}
}

But you probably don't want the last line, you want the last N lines, so use this instead:

public String tail2( File file, int lines) {java.io.RandomAccessFile fileHandler = null;try {fileHandler = new java.io.RandomAccessFile( file, "r" );long fileLength = fileHandler.length() - 1;StringBuilder sb = new StringBuilder();int line = 0;for(long filePointer = fileLength; filePointer != -1; filePointer--){fileHandler.seek( filePointer );int readByte = fileHandler.readByte();if( readByte == 0xA ) {if (line == lines) {if (filePointer == fileLength) {continue;} else {break;}}} else if( readByte == 0xD ) {line = line + 1;if (line == lines) {if (filePointer == fileLength - 1) {continue;} else {break;}}}sb.append( ( char ) readByte );}sb.deleteCharAt(sb.length()-1);String lastLine = sb.reverse().toString();return lastLine;} catch( java.io.FileNotFoundException e ) {e.printStackTrace();return null;} catch( java.io.IOException e ) {e.printStackTrace();return null;}finally {if (fileHandler != null )try {fileHandler.close();} catch (IOException e) {/* ignore */}}
}

Another Example

public static void main(String[] args) throws Exception {int n = 3;List<String> lines = new ArrayList<>();try (RandomAccessFile f = new RandomAccessFile("test", "r")) {ByteArrayOutputStream bout = new ByteArrayOutputStream();for (long length = f.length(), p = length - 1; p > 0 && lines.size() < n; p--) {f.seek(p);int b = f.read();if (b == 10) {if (p < length - 1) {lines.add(0, getLine(bout));bout.reset();}} else if (b != 13) {bout.write(b);}}}System.out.println(lines);
}static String getLine(ByteArrayOutputStream bout) {byte[] a = bout.toByteArray();// reverse bytesfor (int i = 0, j = a.length - 1; j > i; i++, j--) {byte tmp = a[j];a[j] = a[i];a[i] = tmp;}return new String(a);
}