src/org/nutz/lang/Streams.java
public static BufferedOutputStream buff(OutputStream ops) {
        if (ops == null)
            throw new NullPointerException("ops is null!");
        if (ops instanceof BufferedOutputStream)
            return (BufferedOutputStream) ops;
        return new BufferedOutputStream(ops);
    }
public static BufferedOutputStream buff(OutputStream ops) {
        if (ops == null)
            throw new NullPointerException("ops is null!");
        if (ops instanceof BufferedOutputStream)
            return (BufferedOutputStream) ops;
        return new BufferedOutputStream(ops);
    }
为一个输出流包裹一个缓冲流。如果这个输出流本身就是缓冲流，则直接返回

@param ops
输出流。
@return 缓冲输出流