how to do memcpy() in java ?

how to copy the content of a huge byte() (byte array) to another, as we can do in c using memcpy() ?

to be more specific, for example,
byte[] ba1;
byte[] ba2 = new byte[100];

ba1 = new String("how to do memcpy in java");
 
  memcpy(ba2,ba1,ba1.length) <-- how to do this in java ?
    or
  memcpy(ba2[10],ba1,ba1.length) <-- how to do this in java ?