如何正确比较 JUnit 中的两个链表？

Question

I have the following sentence:

assertArrayEquals(Arrays.asList(df.sort("State", new SortDescending())).toArray(),Arrays.asList("[WV, WV, WI, WA, VA, TX, SD, PA, OH, ND, NC, NC, MB, MA, KS, FL, DE]").toArray());

The return of the function is a List< Object > and it contains:

[WV, WV, WI, WA, VA, TX, SD, PA, OH, ND, NC, NC, MB, MA, KS, FL, DE]

The error is:

Expected :java.util.LinkedList<[WV, WV, WI, WA, VA, TX, SD, PA, OH, ND, NC, NC, MB, MA, KS, FL, DE]>
Actual   :java.lang.String<[WV, WV, WI, WA, VA, TX, SD, PA, OH, ND, NC, NC, MB, MA, KS, FL, DE]>

Why i don't pass the test when I compare these two lists?

Answer 1

In Java, " characters specify a String value. Not a List. Just a single String value.

This:

"[WV, WV, WI, WA, VA, TX, SD, PA, OH, ND, NC, NC, MB, MA, KS, FL, DE]"

is not a List. It's a single String object, whose value may happen to look like a List, but it's not a List. It is in double-quotes ( " ), therefore it is a single String object.

This:

Arrays.asList("[WV, WV, WI, WA, VA, TX, SD, PA, OH, ND, NC, NC, MB, MA, KS, FL, DE]")

create a List which contains one element. It is a List<String> with a size of one.

Arrays.asList does not attempt to parse Strings in any way. You cannot specify a List of items inside a single String value.

What you probably meant to write was this:

Arrays.asList("WV", "WV", "WI", "WA", "VA", "TX", "SD", "PA", "OH", "ND", "NC", "NC", "MB", "MA", "KS", "FL", "DE")

Notice that are no [ or ] characters. The List is comprised of individual String values, each specified as a separate argument to Arrays.asList.

You might find it easier to just compare the Lists directly:

Assert.assertEquals("Checking for correctly sorted list.",
    Arrays.asList("WV", "WV", "WI", "WA", "VA", "TX", "SD", "PA", "OH", "ND", "NC", "NC", "MB", "MA", "KS", "FL", "DE"),
    Arrays.asList(df.sort("State", new SortDescending())));