Java IO，

Java IO，

字节流(FileInputStream、DataInputStream、BufferedInputStream、 FileOutputSteam、DataOutputStream、BufferedOutputStream)
字符流 (BufferedReader、InputStreamReader、FileReader、BufferedWriter、 OutputStreamWriter、PrintWriter、FileWriter)

字符流和字节流的区别：

• 字符流按字符读取，字节流按字节读取
• 字符流一般读写文本，字节流一般进行与文本内容无关的操作。

源码分析：

public
class BufferedOutputStream extends FilterOutputStream

    public BufferedOutputStream(OutputStream out) {
        this(out, 8192);
    }

装饰模式

同步

public synchronized void write(byte b[], int off, int len) throws IOException {
        if (len >= buf.length) {
            flushBuffer();
            out.write(b, off, len);
            return;
        }
        if (len > buf.length - count) {
            flushBuffer();
        }
        System.arraycopy(b, off, buf, count, len);
        count += len;
    }

public void write(byte b[], int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if ((off < 0) || (off > b.length) || (len < 0) ||
                   ((off + len) > b.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }
        for (int i = 0 ; i < len ; i++) {
            write(b[off + i]);
        }
    }

public synchronized void write(int b) throws IOException {
        if (count >= buf.length) {
            flushBuffer();
        }
        buf[count++] = (byte)b;
    }

 private void flushBuffer() throws IOException {
        if (count > 0) {
            out.write(buf, 0, count);
            count = 0;
        }
    }

写入缓存，再写入文件