Check if a list of byte arrays contains a new byte array

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I have a list of byte arrays and need to check if this list doesn't contain a new given byte array. If not, than I need to perform some action.

Right now, I'm trying to do it like this:

List<byte[]> listOFByteArrays = getListOfByteArrays();
byte[] newByteArray = getNewByteArray();

if (!listOfByteArrays.contains(newByteArray)){
// do some action

This doesn't work for me, it performs this some action in the if statement anyway.

What am I doing wrong and what is the right way to check it?

Thank you in advance.

List.contains method use equals to check if the list contain specific element. From javadoc:

Returns true if this list contains the specified element. More formally, returns true if and only if this list contains at least one element e such that Objects.equals(o, e).

But for arrays the equals method is the same as ==. That's why contains returns false even if content is the same. Use Arrays.equals instead:

for (byte[] arr : listOfByteArrays) {
    if (Arrays.equals(arr, newByteArray )) {


Java Guava, GBlog � Puzzles � What's New? public static boolean contains(byte[] array, byte target) byte value which is to be checked if it is present in the array or not. import;. import java.util.Arrays; Bean life cycle in Java Spring � Difference between List and ArrayList in� That works perfect and I get the index of the first byte back. But the problem is I want to check very large Data. My "big" Array contains around 900000000 Bytes and my searchArray about 10-20 Bytes. In that way my function is very very slow. Is there a way to make a better performance? I need the Index of every found match so I do it into a loop:

You can try this

if (!listOFByteArrays
    .anyMatch(byteArray -> Arrays.areEqual(byteArray, newByteArray))) {

    // do some action

Java Guava, It contains well written, well thought and well explained computer science and Return Value: This method returns a byte array containing the same values as a Exceptions: This method throws NullPointerException if the passed collection Bytes;. import java.util.Arrays;. import java.util.List;. class GFG {. // Driver's code. This post considers the benefits of branch-free algorithms through the lens of a trivial problem: finding the first position of a byte within an array. While this problem is simple, it has many applications in parsing: BSON keys are null terminated strings; HTTP 1.1 headers are delimited by CRLF sequences; CBOR arrays are terminated by the stop

Java's .contains(T) simply performs an equality check on the argument. An array, however, is not equal to another array containing the same values, because all of the values are not checked and the comparison is done on their pointers.

As you already have two byte[], the gruesome - but functional - way could be to simply... Iterate through the list, and use java.util.Arrays.equals(), which works wonders on primitive arrays.

List<byte[]> listOFByteArrays = getListOfByteArrays();
byte[] newByteArray = getNewByteArray();
boolean flag = false;

for(byte[] b : listOFByteArrays) {
    if(Arrays.equals(b,newByteArray)) { 
       flag = true; 

if (!flag){
   // do stuff

Java.util.Arrays.equals(byte[], byte[]) Method, Arrays.equals(byte[] a, byte[] a2) method returns true if the two specified arrays of bytes Two arrays are equal if they contain the same elements in the same order. Two array references are considered equal if both are null. public static void main(String[] args) { // initializing three byte arrays byte[] arr1 = new byte[] { 12, 31� Return url. Output parameter - CollectionType should be set to OracleCollection. Just a mapping from a C# byte array to a uint8_t C++ array, with an additional parameter for the number of elements. You would then have an array of byte arrays. ru (Maxim Dounin) Date: Fri, 01 Apr 2016 01:18:28 +0000 Subject: [nginx] Trailing space fix.

You're looking for:

for (int i = 0; i < listOfByteArrays.size(); i++) {
    if (Arrays.equals(newByteArray, listOfByteArrays.get(i))) {
        //do some action

ArrayUtils (Apache Commons Lang 3.11 API), However, an Object array that contains a null element may throw an exception. Each method documents its The index value when an element is not found in a list or array: -1 . Copies the given array and adds the given element at the end of the new array. this method has been superseded by insert(int, byte[], byte. Anyone know a good and effective way to search/match for a byte pattern in an byte[] array and then return the positions. For example byte[] pattern = new byte[] {12,3,5,76,8,0,6,125}; byte[]

Python bytes(), If you want to use the mutable version, use bytearray() method. bytes() Parameters. bytes() takes three optional parameters: source (Optional) - source to initialize� User to user discussions about the PB/Win (formerly PB/DLL) product line. Discussion topics include PowerBASIC Forms, PowerGEN and PowerTree for Windows.

Converting Between Byte Arrays and Hexadecimal Strings in Java , Learn how to convert between hexadecimal strings and byte arrays using the I just announced the new Learn Spring course, focused on the ways to convert a byte array to a hexadecimal String, and vice versa. First of all, we need to check if the length of the hexadecimal String is an even number. If you're using the actual class System.Collections.Generic.List<byte>, call ToArray(). It returns a new byte[].

How to convert Byte[] array to String in Java, In Java, we can use new String(bytes, StandardCharsets.UTF_8) to toString is working properly if you see the documentation you will know. This article will explain Firebase's array support, the ins-and-outs of arrays in distributed data, and some common techniques for dealing with array-like data. least-significant to most-significant bit or vice versa) and any convenient byte-wise way (eg first element in a byte list to last or vice versa, least--significant to most-significant

  • Of course it performs.. Your list doesn't contain newByteArray
  • An array is only equal to itself. So your list can't possibly contain newByteArray (unless newByteArrayis not a new byte array, but one of the arrays stored in the list). You need to loop through the list and compare the contents of the byte arrays:…
  • @JBNizet Yes, you are right. I have to compare contents. Thank you!
  • It can be modifeid like this: if (bytesPhotosInCloud .stream() .noneMatch(byteArray -> Arrays.equals(byteArray, bytesImage))){ //do some action } Thank you.
  • Why are you using Boolean objects instead of straight-forward boolean values?
  • @Holger Pure force of habit, it serves no purpose here. I will edit it out.