类分层结构
- java.lang.Object
- java.io.File
- java.io.InputStream
- java.io.FileInputStream
- java.io.FilterInputStream
- java.io.BufferedInputStream
- java.io.DataInputStream
- java.io.OutputStream
- java.io.FileOutputStream
- java.io.FilterOutputStream
- java.io.BufferedOutputStream
- java.io.DataOutputStream
- java.io.PrintStream
- java.io.RandomAccessFile
- java.io.Reader
- java.io.BufferedReader
- java.io.InputStreamReader
- java.io.FileReader
- java.io.Writer
- java.io.BufferedWriter
- java.io.OutputStreamWriter
- java.io.FileWriter
- java.io.PrintWriter
