How to reverse the byte array in java?

Question

Possible Duplicate:
How do I reverse an int array in Java?

What is the equivalent function in java to perform Array.Reverse(bytearray) in C# ?

http://stackoverflow.com/questions/2137755/how-do-i-reverse-an-int-array-in-java — Alex, Oct 15 '12 at 10:33
http://www.java2s.com/Code/Java/Collections-Data-Structure/Reversestheorderofthegivenbytetypearray.htm — maxstreifeneder, Oct 15 '12 at 10:37
Can you say why you need to do this because if you want to switch between little endian and big endian there are much better ways of doing this? — Peter Lawrey, Oct 15 '12 at 10:51
Actually, we are trying to decrypt the .net encrypted string(RSA).In that, we faced some padding issue.To resolve, we wanted to reverse the byte array.For more information click [here](http://stackoverflow.com/questions/12543933/bad-padding-exception-in-java-rsa-decryption) — sat, Oct 15 '12 at 11:38

score 22 · Answer 1 · answered Oct 15 '12 at 10:36

public static void reverse(byte[] array) {
      if (array == null) {
          return;
      }
      int i = 0;
      int j = array.length - 1;
      byte tmp;
      while (j > i) {
          tmp = array[j];
          array[j] = array[i];
          array[i] = tmp;
          j--;
          i++;
      }
  }

Rohit Jain · Answer 2 · 2012-10-15T11:09:28.250

14

You can use Collections.reverse on a list returned by Arrays.asList operated on an Array: -

    Byte[] byteArr = new Byte[5];

    byteArr[0] = 123; byteArr[1] = 45;
    byteArr[2] = 56;  byteArr[3] = 67;
    byteArr[4] = 89;

    List<Byte> byteList = Arrays.asList(byteArr); 

    Collections.reverse(byteList);  // Reversing list will also reverse the array

    System.out.println(byteList);
    System.out.println(Arrays.toString(byteArr));

OUTPUT: -

[89, 67, 56, 45, 123]
[89, 67, 56, 45, 123]

UPDATE: - Or, you can also use: Apache Commons ArrayUtils#reverse method, that directly operate on primitive type array: -

byte[] byteArr = new byte[5];
ArrayUtils.reverse(byteArr);

edited Oct 15 '12 at 11:09

answered Oct 15 '12 at 10:35

Rohit Jain

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@MarkoTopolnik Didn't knew that. At first I thought you meant something else. Thanks. Edited. :) – Rohit Jain Oct 15 '12 at 10:52
And as a convenience, it is most practical to print an array's contents using `Arrays.toString(array)`. – Marko Topolnik Oct 15 '12 at 10:57
@MarkoTopolnik Okay. I always used array.toString() and got wierd `HashCodes`.. :( Thanks a million for that.. – Rohit Jain Oct 15 '12 at 10:58

score 2 · Answer 3 · answered Oct 15 '12 at 10:37

2

You may use java.util.Collections.reverse(). It takes java.util.List as an input argument. So you should convert your byteArray into a List either by doing Arrays.asList(byteArray) or by creating an List object and adding byte values into it.

answered Oct 15 '12 at 10:37

sakthisundar

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How to reverse the byte array in java?

3 Answers3

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