Use non-JNI method for read(byte[])

[xerial]

For avoiding JNI overhead, reported in apache/spark#12074

[SaintBacchus]

Hi @xerial , I notice that System.arraycoy is also a native method, and how can this modify reduce the JNI calls reported in spark?

    public static native void arraycopy(Object src,  int  srcPos,
                                        Object dest, int destPos,
                                        int length);

[ijuma]

@SaintBacchus arraycopy is usually a VM intrinsic and it doesn't incur JNI overhead (that's the case for HotSpot for example).

[xerial]

@SaintBacchus As @ijuma mentioned, VM intrinsic native code has no overhead compared to user defined one.