CODEWITHSUNDEEP
groovyarrays
Grammin
Grammin

Reputation: 12205

Cannot create an array of byte arrays in groovy

I'm getting an error when I try to create an array of byte arrays in groovy. My code is:

def patch0 = [0, 2, 4, 8, 16] as byte[];
def patch1 = [0, 3, 6, 12, 24] as byte[];

def patches = [patch0, patch1] as byte[];

The error I'm getting is: 

GroovyCastException: Cannot cast object '[B@7630e551' with class '[B' to class 'java.lang.Number'

Upvotes: 2

Views: 1642

Answers (2)

Rob Cannon
Rob Cannon

Reputation: 392

I think your problem is that when you cast the array to a byte[] in the third line, Groovy is trying to cast each array to a byte. If you change that cast to a two-dimensional byte array the error goes away.

def patch0 = [0, 2, 4, 8, 16] as byte[]
def patch1 = [0, 3, 6, 12, 24] as byte[]

def patches = [patch0, patch1] as byte[][]

Upvotes: 5

Seagull
Seagull

Reputation: 13859

Problem is, that [patch0, patch1] is an array of byte[] arrays. It's not an array concatenation. Its [[0, 2, 4, 8, 16], [0, 3, 6, 12, 24]] which cannot be cast to byte[]

You could use flatten() method like 

def p = [patch0, patch1].flatten() as byte[]

Or do smth like 

((patch0 as List) + (patch1 as List) ) as byte[]

Or you can ommit a cast

def patch0 = [0, 2, 4, 8, 16] // will be Collection instance
def patch1 = [0, 3, 6, 12, 24]
(patch0 + patch1) as byte[] // You can plus collections, and then cast.

Versions above is Groovyer, but may be not as optimal.

Maybe faster solution will be smth from, How can I concatenate two arrays in Java? but most of all solutions there are verbose, Java-way, or use external libraries like ApacheCommon

Or look a t specific byte array Java concatenation. Easy way to concatenate two byte arrays

Upvotes: 2

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