NSData methods equivalent in Java

Question

I am trying to match iOS code to Java code, and I run into the problem. I read all the answers and as far as I understood I need to use ByteBuffer as an equivalent to NSData in Swift. But I couldn't find the methods that will help me to achieve this logic.

1. In Java I need to initializes an object filled with a given number of bytes copied from a given buffer, like in this code let data = NSData(bytes: array, length: 4)

2. As a second step I need to get a copy a number of bytes from the start of the data object into a given buffer, like in this array. data.getBytes(&value, length: 4).

Will appreciate any help.