Compare List<String>

I have two List<String[]>'s (string array lists), and I'd like to match the contents with each other. Obviously == doesn't do the trick, but .equals () doesn't seem to do it either. So how should I check whether the contents of the string array lists are the same?

By the way, in both above cases I got an exception with message null.

EDIT: Ok... for some reason only x.equals(y) works, and not y.equals(x). Odd...


Perhaps the easiest solution would be to use two List<List<String>>s instead. Assuming the List implementations used extend AbstractList, using equals will give you the desired behavior. From the documentation for AbstractList.equals:

Compares the specified object with this list for equality. Returns true if and only if the specified object is also a list, both lists have the same size, and all corresponding pairs of elements in the two lists are equal. (Two elements e1 and e2 are equal if (e1==null ? e2==null : e1.equals(e2)).) In other words, two lists are defined to be equal if they contain the same elements in the same order.

You can easily wrap a String[] in a thin List<String> implementation that extends AbstractList by using Arrays.asList.

EDIT: Here's an example:

String[] array1 = {"1", "2", "3"};
String[] array2 = {"4", "7"};

String[] array3 = {"1", "2", "3"};
String[] array4 = {"4", "7"};

List<List<String>> lst1 = new ArrayList<>();

List<List<String>> lst2 = new ArrayList<>();

System.out.println(lst1.equals(lst2)); //prints true

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