地图的地图根据内部地图的值获取外部地图

Question

How do I write below code using Java8?

for (Entry<Integer, Map<String, Object>> entry : data.entrySet()) {
  Map<String, Object> value = entry.getValue();
  if (value.get(Constants.USER_TRAN_ID).equals(stsTxn.getSeedTrade().getTransactionId())) {
    closedTaxLotByTxnId = value;
    break;
  }
}

I am clueless after this

data.values().stream().map(e -> e.get(Constants.USER_TRAN_ID)).filter(txnId -> txnId.equals(stsTxn.getSeedTrade().getTransactionId()));

Answer 1

You don't need map . Just use filter with your criteria, and findFirst as terminal operation:

Optional<Map<String, Object>>
    value = data.values()
                .stream()
                .filter(m -> m.get(Constants.USER_TRAN_ID).equals(stsTxn.getSeedTrade().getTransactionId()))
                .findFirst();

If you want a default value (such as null) when no match is found, use:

Map<String, Object> closedTaxLotByTxnId =
           data.values()
               .stream()
               .filter(m -> m.get(Constants.USER_TRAN_ID).equals(stsTxn.getSeedTrade().getTransactionId()))
               .findFirst()
               .orElse(null);