将带有 If 语句的 For 循环转换为流

Question

我想将以下带有if-statement 的for-loop 转换为Stream。

public Integer months() {
    
    String desiredObject = // initialize somehow
    Map<String, Integer> monthDays = new HashMap<>();
    
    monthDays.put("March", 31);
    monthDays.put("April", 30);
    
    Set<Map.Entry<String, Integer>> entrySet = monthDays.entrySet();
    
    for (Map.Entry<String, Integer> pair : entrySet) {
        if (desiredObject.equals(pair.getKey())) {
            return pair.getValue();
        }
    }
}

怎么做？

Answer 1

return entrySet.stream()
  .filter(pair -> desiredObject.equals(pair.getKey()))
  .map(Entry::getValue)
  .findAny().orElse(null);

或者，或者只是

return monthDays.get(desiredObject);