一、IO的类型
面向字节的流，面向字符的流
二、面向字节的流
（1）InputStream
FileInputStream
FilterInputStream
-BufferedInputStream
-DataInputStream
-PushbackInputStream 回退流 unread()
ObjectInputStream
PipedInputStream
ByteArrayInputStream
SequenceInputStream 合并流
StringBufferInputStream 过时的类，使用ByteArrayInputStream代替
（2）OutputStream
FileOutputStream
FilterOutputStream
-BufferedOutputStream
-DataOutputStream
-PrintStream
ObjectOutputStream
PipedOutputStream
ByteArrayOutputStream
三、字符流
（1）Reader
BufferedReader
-LineNumberReader
InputStreamReader
-FileReader
StringReader
PipedReader
CharArrayReader
FilterReader
-PushbackReader
（2）Writer
BufferedWriter
OutputStreamWriter
-FileWriter
StringWriter
PipedWriter
CharArrayWriter
FilterWriter
PrintWriter