Java中的IO分为两大线，字节流和字符流

字节流基类：InputStream/OutputStream 操作byte[]的

I部分：

public abstract int read() throws IOException;

O部分：

public abstract void write(int b) throws IOException;

字符流基类：Reader/Writer 操作char[]的

I部分：

abstract public void close() throws IOException;abstract public int read(char cbuf[], int off, int len) throws IOException;

O部分：

abstract public void write(char cbuf[], int off, int len) throws IOException;abstract public void flush() throws IOException;abstract public void close() throws IOException;

转换桥梁：

InputStreamReader和OutputStreamWriter