Swapping switch-case in extra fle/data structure (Java)

Question

Hi guys,

it may be a nooby question, but I've never needed it before:

I have several strings and I want to compare them to given ones...

At first glance it would lead to a switch/case construction in what every available entry is checked.

Is there a more elegant way to swap those strings as key/value datas?

greets, poeschlorn

Answer 1

Update: My bad. I misread this as case insensitive search.

Case sensitive is easy. Java does not yet support Strings in switch statements. The easiest solution is:

if (string1.equals(string2)) {
  ...
} else if (string1.equals(string3)) {
  ...
}

Or as a loop:

String[] matches = new String[] {
  "abcd",
  "efgh",
  "ijkl"
};

for (String match : matches) {
  if (matches.equals(string)) {
    ...
  }
}

Of course, this is linear (O(n)) and doesn't scale but is simple and is sufficient for the simplest of cases. A better solution is to use a hash-based lookup:

Set<String> matches = new HashSet<String>();
matches.add("abcd");
matches.add("efgh");
matches.add("ijkl");

if (matches.contains(string1)) {
  ...
}

This is near-linear (O(1)) lookup and will scale much better with a large number of Strings.

Answer 2

Yes, use the strings as keys in a HashMap, and have the corresponding values be objects defining the action to take if the key has been matched, unless you only have one behavior, in which case you can simply use a HashSet, test if the string is in the set, and then take action accordingly.