Compare two Byte Arrays Java

Question

I have a byte array with a  known binary sequence in it  I need to confirm that the binary sequence is what it s supposed to be  I have tried  equals in addition to     but neither worked    byte   array   new BigInteger  1111000011110001   2  toByteArray    if  new BigInteger  1111000011110001   2  toByteArray      array       System out println  the same      else       System out println  different

User · Answer

Java doesn t overload operators  so you ll usually need a method for non-basic types  Try the Arrays equals   method

User · Answer

Check out the static java util Arrays equals   family of methods  There s one that does exactly what you want

User · Answer

Since I wanted to compare two arrays for a unit Test and I arrived on this answer I thought I could share   You can also do it with    Test public void testTwoArrays       byte   array   new BigInteger  1111000011110001   2  toByteArray      byte   secondArray   new BigInteger  1111000011110001   2  toByteArray       Assert assertArrayEquals array  secondArray       And you could check on Comparing arrays in JUnit assertions for more infos

User · Answer

In your example  you have   if  new BigInteger  1111000011110001   2  toByteArray      array    When dealing with objects     in java compares reference values  You re checking to see if the reference to the array returned by toByteArray   is the same as the reference held in array  which of course can never be true  In addition  array classes don t override  equals   so the behavior is that of Object equals   which also only compares the reference values    To compare the contents of two arrays  static array comparison methods are provided by the Arrays class  byte   array   new BigInteger  1111000011110001   2  toByteArray    byte   secondArray   new BigInteger  1111000011110001   2  toByteArray    if  Arrays equals array  secondArray         System out println  Yup  they re the same

User · Answer

You can use both Arrays equals   and MessageDigest isEqual    These two methods have some differences though   MessageDigest isEqual   is a time-constant comparison method and Arrays equals   is non time-constant and it may bring some security issues if you use it in a security application   The details for the difference can be read at Arrays equals   vs MessageDigest isEqual

User · Answer

Of course  the accepted answer of Arrays equal  byte   first  byte   second   is correct  I like to work at a lower level  but I was unable to find a low level efficient function to perform equality test ranges  I had to whip up my own  if anyone needs it   public static boolean ArraysAreEquals   byte   first   int firstOffset   int firstLength   byte   second   int secondOffset   int secondLength         if  firstLength    secondLength             return false             for  int index   0  index  lt  firstLength    index             if  first firstOffset index     second secondOffset index                 return false                       return true

[java] Compare two Byte Arrays? (Java)

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