snippet to get a list of Salesforce Communities in APEX

communities.cls

List<Network> communities = [ SELECT Id, Name, UrlPathPrefix, Status FROM Network ];

for (Network community : communities) {
    System.debug(community.Name + ': ' + community);
}

// or via Connect API

List<ConnectApi.Community> communitiesConnect = ConnectApi.Communities.getCommunities().communities;
for ( ConnectApi.Community community : communitiesConnect) {
    System.debug(community.name + ': ' + community);
}