Try the following code:
public static byte[] decode(String hex){
String[] list=hex.split("(?<=\\G.{2})");
ByteBuffer buffer= ByteBuffer.allocate(list.length);
System.out.println(list.length);
for(String str: list)
buffer.put(Byte.parseByte(str,16));
return buffer.array();
}
To convert to String just create a new String with the byte[] returned by the decode method.