Translating java DFS algorithm code to Dart - flutter

Question

I've been doing some research to find a suitable algorithm for suggesting friends. I came across DFS, but I've never implemented it in Dart before. Could someone please help me t translate it into Dart? Below is the java code:
public class SuggestFriendsDFS<T> {
private HashMap<T, ArrayList<T>> adj = new HashMap<>(); //graph
private List<Set<T>> groups = new ArrayList<>();
public void addFriendship(T src, T dest) {
adj.putIfAbsent(src, new ArrayList<T>());
adj.get(src).add(dest);
adj.putIfAbsent(dest, new ArrayList<T>());
adj.get(dest).add(src);
}
//V is total number of people, E is number of connections
private void findGroups() {
Map<T, Boolean> visited = new HashMap<>();
for (T t: adj.keySet())
visited.put(t, false);
for (T t:adj.keySet()) {
if (!visited.get(t)) {
Set<T> group = new HashSet<>();
dfs(t, visited, group);
groups.add(group);
}
}
}
//DFS + memoization
private void dfs(T v, Map<T, Boolean> visited, Set<T> group ) {
visited.put(v,true);
group.add(v);
for (T x : adj.get(v)) {
if (!visited.get(x))
dfs(x, visited, group);
}
}
public Set<T> getSuggestedFriends (T a) {
if (groups.isEmpty())
findGroups();
Set<T> res = new HashSet<>();
for (Set<T> t : groups) {
if (t.contains(a)) {
res = t;
break;
}
}
if (res.size() > 0)
res.remove(a);
return res;
}
}
I'm aware it's too much to ask, but any help will be much appreciated as I tried to translate it and ended up getting loads of errors. Thanks in advance!(: For reference, this is where I found the explanation for the java code.

Answer 1

I tried https://sma.github.io/stuff/java2dartweb/java2dartweb.html that does automatic Java to Dart conversion but it doesn't work well as soon as the code is a bit complex.
See the full conversion below, you can try it in Dartpad
import 'dart:collection';
class SuggestFriendsDFS<T> {
final HashMap<T, List<T>> _adj = HashMap(); //graph
final List<Set<T>> groups = [];
//Time O(1), Space O(1)
void addFriendship(T src, T dest) {
_adj.putIfAbsent(src, () => <T>[]);
_adj[src]!.add(dest);
_adj.putIfAbsent(dest, () => <T>[]);
_adj[dest]!.add(src);
}
//DFS wrapper, Time O(V+E), Space O(V)
//V is total number of people, E is number of connections
void findGroups() {
Map<T, bool> visited = HashMap();
for (T t in _adj.keys) {
visited[t] = false;
}
for (T t in _adj.keys) {
if (visited[t] == false) {
Set<T> group = HashSet();
_dfs(t, visited, group);
groups.add(group);
}
}
}
//DFS + memoization, Time O(V+E), Space O(V)
void _dfs(T v, Map<T, bool> visited, Set<T> group) {
visited[v] = true;
group.add(v);
for (T x in _adj[v] ?? []) {
if ((visited[x] ?? true) == false) _dfs(x, visited, group);
}
}
//Time O(V+E), Space O(V)
Set<T> getSuggestedFriends(T a) {
if (groups.isEmpty) findGroups();
var result = groups.firstWhere((element) => element.contains(a),
orElse: () => <T>{});
if (result.isNotEmpty) result.remove(a);
return result;
}
}
void main() {
SuggestFriendsDFS<String> g = SuggestFriendsDFS();
g.addFriendship("Ashley", "Christopher");
g.addFriendship("Ashley", "Emily");
g.addFriendship("Ashley", "Joshua");
g.addFriendship("Bart", "Lisa");
g.addFriendship("Bart", "Matthew");
g.addFriendship("Christopher", "Andrew");
g.addFriendship("Emily", "Joshua");
g.addFriendship("Jacob", "Christopher");
g.addFriendship("Jessica", "Ashley");
g.addFriendship("JorEl", "Zod");
g.addFriendship("KalEl", "JorEl");
g.addFriendship("Kyle", "Lex");
g.addFriendship("Kyle", "Zod");
g.addFriendship("Lisa", "Marge");
g.addFriendship("Matthew", "Lisa");
g.addFriendship("Michael", "Christopher");
g.addFriendship("Michael", "Joshua");
g.addFriendship("Michael", "Jessica");
g.addFriendship("Samantha", "Matthew");
g.addFriendship("Samantha", "Tyler");
g.addFriendship("Sarah", "Andrew");
g.addFriendship("Sarah", "Christopher");
g.addFriendship("Sarah", "Emily");
g.addFriendship("Tyler", "Kyle");
g.addFriendship("Stuart", "Jacob");
g.findGroups();
print(g.groups);
String name = "Andrew";
print("Suggestion friends of " +
name +
": " +
g.getSuggestedFriends(name).toString());
}