包含字节数组列表的方法

Question

so i have a list List<byte[]> lets say "fullList", whereby some other piece of code generates another List containing some byte[] partialList. so i use the .contain method which always fails for searching got byte[] in partialList from the fullList. Why is this??

List<byte[]> fullList = {some byte[] arrays added here..}
List<byte[]> partialList = {some byte[] arrays added here..}

byte[] toCheck = partialList.get(0);
System.out.println("The check is "+ fullList.contains(tocheck));

Answer 1

The problem is that Java arrays do not implement equals properly , ie two arrays are considered "equal" only if their memory address is the same, ie if they are the exact same object reference.

byte[] foo = {1,2,3};
byte[] bar = {1,2,3};
System.out.println(foo.equals(bar)); // prints 'false'

To work around this problem, you could either encode those byte[] as numbers and use List<Integer> (or Long ) instead, or implement your own contains method using Arrays.equals

boolean contains(List<byte[]> arrays, byte[] other) {
    for (byte[] b : arrays)
        if (Arrays.equals(b, other)) return true;
    return false;
}