public Map<Long, String> getIdNameMap(List<Account> accounts) {
return accounts.stream().collect(Collectors.toMap(Account::getId, Account::getUsername));
}
public Map<Long, Account> getIdAccountMap(List<Account> accounts) {
return accounts.stream().collect(Collectors.toMap(Account::getId, account -> account));
}
public Map<String, Account> getNameAccountMap(List<Account> accounts) {
return accounts.stream().collect(Collectors.toMap(Account::getUsername, Function.identity(), (key1, key2) -> key2));
}