二、使用Okio框架进行输出操作(Sink)

Sink相当于输出流（OutputStream），把内存中的内容输出到硬盘。



关于Flushable、Closeable 、AutoCloseable接口的说明，请参考以下文档：
探究java IO之AutoCloseable,Closeable和Flushable接口
例子：

try {
File file = new File("test.txt"); //如果文件不存在，则自动创建
BufferedSink sink = Okio.buffer(Okio.sink(file));
sink.writeUtf8("Hello, World");
sink.writeString("测试信息", Charset.forName("UTF-8"));
sink.close();
} catch (IOException e) {
e.printStackTrace();
}

BufferedSink API

/**
* 返回Sink内部的Buffer.
*/
Buffer buffer();

/**
* 写ByteString中的数据到Sink
*/
BufferedSink write(ByteString byteString) throws IOException;

/**
* 写字节数组到Sink。类似OutputStream#write(byte[])
*/
BufferedSink write(byte[] source) throws IOException;

/**
* 将指定 byte 数组中从偏移量off开始的len个字节写入Sink。类似
* OutputStream#write(byte[], int, int)
*/
BufferedSink write(byte[] source, int offset, int byteCount) throws IOException;

/**
* 从Source中移除所有的字节，把他们写入到Sink中，返回读取的字节数。如果Source中      * 的内容已被读取，则返回0。
*/
long writeAll(Source source) throws IOException;

/**
* 从Source中移除byteCount字节，并把他们写入到Sink中
*/
BufferedSink write(Source source, long byteCount) throws IOException;

/**
* 以UTF-8编码把内容写入到Sink中
*/
BufferedSink writeUtf8(String string) throws IOException;

/**
* 以charset编码把内容写入到Sink中
*/
BufferedSink writeString(String string, Charset charset) throws IOException;

/**
* Writes a byte to this sink.
*/
BufferedSink writeByte(int b) throws IOException;

/**
* Writes a big-endian short to this sink using two bytes.
*/
BufferedSink writeShort(int s) throws IOException;

/**
* Writes a little-endian short to this sink using two bytes.
*/
BufferedSink writeShortLe(int s) throws IOException;

/**
* Writes a big-endian int to this sink using four bytes.
*/
BufferedSink writeInt(int i) throws IOException;

/**
* Writes a little-endian int to this sink using four bytes.
*/
BufferedSink writeIntLe(int i) throws IOException;

/**
* Writes a big-endian long to this sink using eight bytes.
*/
BufferedSink writeLong(long v) throws IOException;

/**
* Writes a little-endian long to this sink using eight bytes.
*/
BufferedSink writeLongLe(long v) throws IOException;

/**
* Writes a long to this sink in signed decimal form (i.e., as a string in base 10).
*/
BufferedSink writeDecimalLong(long v) throws IOException;

/**
* Writes a long to this sink in hexadecimal form (i.e., as a string in base 16).
*/
BufferedSink writeHexadecimalUnsignedLong(long v) throws IOException;

/**
* Writes complete segments to the underlying sink, if one exists. Like {@link #flush}, but
* weaker. Use this to limit the memory held in the buffer to a single segment.
*/
BufferedSink emitCompleteSegments() throws IOException;

/**
* Writes all buffered data to the underlying sink, if one exists. Like {@link #flush}, but
* weaker. Call this before this buffered sink goes out of scope so that its data can reach its
* destination.
*/
BufferedSink emit() throws IOException;

/**
* 返回Sink中的输出流.
*/
OutputStream outputStream();

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