java8_example_3.java

  // Traditional Method
  List<Transaction> groceryTransactions = new Arraylist<>();
  for(Transaction t: transactions){
    if(t.getType() == Transaction.GROCERY){
      groceryTransactions.add(t);
    }
  }
  Collections.sort(groceryTransactions, new Comparator(){
    public int compare(Transaction t1, Transaction t2){
      return t2.getValue().compareTo(t1.getValue());
    }
  });
  List<Integer> transactionIds = new ArrayList<>();
  for(Transaction t: groceryTransactions){
    transactionsIds.add(t.getId());
  }


  // Using Stream API
  List<Integer> transactionsIds = 
    transactions.stream()
                .filter(t -> t.getType() == Transaction.GROCERY)
                .sorted(comparing(Transaction::getValue).reversed())
                .map(Transaction::getId)
                .collect(toList());