public class FileWriter
extends OutputStreamWriter

Convenience class for writing character files. The constructors of this class assume that the default character encoding and the default byte-buffer size are acceptable. To specify these values yourself, construct an OutputStreamWriter on a FileOutputStream.
Whether or not a file is available or may be created depends upon the underlying platform. Some platforms, in particular, allow a file to be opened for writing by only one FileWriter (or other file-writing object) at a time. In such situations the constructors in this class will fail if the file involved is already open.
FileWriter is meant for writing streams of characters. For writing streams of raw bytes, consider using a FileOutputStream.

public class OutputStreamWriter
extends Writer

An OutputStreamWriter is a bridge from character streams to byte streams: Characters written to it are encoded into bytes using a specified charset. The charset that it uses may be specified by name or may be given explicitly, or the platform's default charset may be accepted.
Each invocation of a write() method causes the encoding converter to be invoked on the given character(s). The resulting bytes are accumulated in a buffer before being written to the underlying output stream. The size of this buffer may be specified, but by default it is large enough for most purposes. Note that the characters passed to the write() methods are not buffered.
For top efficiency, consider wrapping an OutputStreamWriter within a BufferedWriter so as to avoid frequent converter invocations. For example:
Writer out
= new BufferedWriter(new OutputStreamWriter(System.out));

public class FileReader
extends InputStreamReader

Convenience class for reading character files. The constructors of this class assume that the default character encoding and the default byte-buffer size are appropriate. To specify these values yourself, construct an InputStreamReader on a FileInputStream.
FileReader is meant for reading streams of characters. For reading streams of raw bytes, consider using a FileInputStream.

public class InputStreamReader
extends Reader

An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and decodes them into characters using a specified charset. The charset that it uses may be specified by name or may be given explicitly, or the platform's default charset may be accepted.
Each invocation of one of an InputStreamReader's read() methods may cause one or more bytes to be read from the underlying byte-input stream. To enable the efficient conversion of bytes to characters, more bytes may be read ahead from the underlying stream than are necessary to satisfy the current read operation.
For top efficiency, consider wrapping an InputStreamReader within a BufferedReader. For example:
BufferedReader in
= new BufferedReader(new InputStreamReader(System.in));