Multiple Predicates to group collection to hashmap - java-8

Question

I have a list of Objects as below -
List<Transaction>
where the Transaction Object will look like
Transaction {
String Status;
}
Status <A,B,C,D,E,F,G...>
If Status in (A,B,C)->Success
If Status in (D,E,F)->Failure
If Status in (G,H...)->Pending
Individual Predicates for identifying each status transaction are defined.
Expected output would be a hashmap with the Success/Failure/Rejected text as key and collective count of these statuses as value
HashMap<String, Integer> ->
{
"Success": 1,
"Failure":2,
"Pending":2
}
I am unable to proceed how to do this in a single execution. Right now, I get the counts separately. Can anyone please assist with the request?

Answer 1

You may first declare an enum like this to represent the 3 states that you are interested in.
public enum TxStatus {
Success, Failure, Pending;
}
Then write a method in Transaction to transform the String literal value into a real status value that you expect. Here's a one such implementation.
public class Transaction {
private final String status;
private Pattern SUCCESS_PATTERN = Pattern.compile("[ABC]");
private Pattern FAILURE_PATTERN = Pattern.compile("[DEF]");
private Pattern PENDING_PATTERN = Pattern.compile("[GHI]");
public Transaction(String status) {
super();
this.status = status;
}
public String getStatus() {
return status;
}
public TxStatus interpretStatus() {
if (SUCCESS_PATTERN.matcher(status).matches()) {
return TxStatus.Success;
}
if (FAILURE_PATTERN.matcher(status).matches()) {
return TxStatus.Failure;
}
if (PENDING_PATTERN.matcher(status).matches()) {
return TxStatus.Pending;
}
throw new IllegalArgumentException("Invalid status value.");
}
}
Finally your client code should look something like this,
Map<String, Long> txStatusToCountMap = txs.stream()
.collect(Collectors.groupingBy(tx -> tx.interpretStatus().toString(),
Collectors.counting()));