byte[] operations in Java

Question

Let's say I have array of bytes:

byte[] arr = new byte[] { 0, 1, 2, 3, 4 };

Does platform has functions that I can use to play with this array - for example, how to invert it (get 4,3,2,1,0)? Or, how to invert part of it (2,1,0,3,4)? Get part of array (0,1,2,3)?

I know I can manually write functions but I am curious if I'm missing useful util functions in platform that I should know about (and couldn't find any useful guide using google).

Thanks!

Answer 1

There are some static methods in the Arrays class (which i don't know availability of on dalvik/android)

Answer 2

java.util.Arrays contains a couple of helper methods (sort(), equals(), fill(), toString()). If that isn't sufficient, you can convert the byte primitive to a Byte object (create a new array) and use new ArrayList (Arrays.asList()) to get a collection which you can modify with the many methods from java.util.Collections.

If you look outside of the RT, there is Commons Primitives:

Commons Primitives provides a library of collections and utilities specially designed for use with primitive types.

Another option is the guava-libraries project which has some support for primitives as well:

This project contains several of Google's core Java libraries that we use in our myriad Java projects.

Answer 3

java.util.Arrays has some array-related utility methods in the standard API. ArrayUtils from Apache Commons Lang has a lot more.

Note however, that Java does not have the concept of array slices as "views", i.e. a "part of an array" returned by such a method will always be a copy.