RandomAccessFile

RandomAccessFile encapsulates a random-access file.

It is not derived from InputStream or OutputStream.

Instead, it implements the interfaces DataInput and DataOutput, which define the basic I/O methods.

It implements the Closeable interface.

RandomAccessFile supports positioning requests, you can position the file pointer within the file.

It has these two constructors:

RandomAccessFile(File fileObj, String access) throws FileNotFoundException: fileObj specifies the name of the file to open as a File object.
RandomAccessFile(String filename, String access) throws FileNotFoundException: the name of the file is passed in filename.

access parameter determines what type of file access is permitted.

access	Meaning
r	the file can be read, but not written.
rw	opened in read-write mode.
rws	opened for read-write operations and every change (data and metadata) will be immediately written to the physical device.
rwd	opened for read-write operations and every change to the file's data will be immediately written to the physical device.

The method seek( ) sets the current position of the file pointer within the file:


void seek(long newPos) throws IOException

newPos specifies the new position, in bytes, of the file pointer from the beginning of the file. After a call to seek( ), the next read or write operation will occur at the new file position.

It includes some additional methods.

One is setLength( ). It has this signature:


void setLength(long len) throws IOException

This method sets the length of the invoking file to that specified by len. This method can be used to lengthen or shorten a file. If the file is lengthened, the added portion is undefined.