更新list1中的参数 <object> 来自list2 <object> 通过使用java 8

Question

I have two list of objects accounts and salaries and I need to iterate the list of objects. If the id matches I need to update the account object.

I have list1 and list2 these two objects are different object type. we need to update the object(param) in list1 with list2 object(param).

Example

if(accounts !=null && salaries!=null) { // checking for nulls
    for (Account obj1 : accounts) {// iterating objects
        for (Salary obj2 : salaries) {
            String id = ibj2.getId();
            if (id.equals(obj1.getId())) {// id checks  
                obj1.setxxxx(obj2.getxxxx());// set the value
            }
        }
    }
}  

I tried:

list1.stream().flatMap(x -> list2 .stream() .filter(y -> x.getId().equals(y.getId())));

Answer 1

Your flatMap (suggested in the comment), will produce a Stream<Salary> , which won't allow you do modify the corresponding Account instances.

You can create a Stream of Account s and their corresponding Salary and run forEach on that Stream :

accounts.stream()
        .flatMap(a->salaries.stream()
                            .filter(s -> s.getID().equals(a.getID())
                            .map(s -> new SimpleEntry<Account,Salary)(a,s)))
        .forEach(e -> e.getKey().setxxxx(e.getValue().getxxxx()));

Answer 2

The final operation, obj1.setxxxx(obj2.getxxxx()); requires to have both obj1 and obj2 . that dictates the item that is streamed from both lists

list1.stream()
    .forEach(obj1 -> 
        list2.stream()
            .filter(obj2 -> obj1.getId().equals(obj2.getId()))
            .findFirst()
            .ifPresent(obj2 -> obj1.setxxxx(obj2.getxxxx()))
    );

Answer 3

I would always suggest to create a Map since the lookup cost will decrease and it will become more readable.

Map<String, List<Salary>> salaryById = salaries.stream().collect(Collectors.groupingBy(Salary::getId));
accounts.forEach(a -> CollectionUtils.emptyIfNull(salaryById.get(a.getId())).forEach(s -> s.setxxxx(..)));

In case Account Salary <-> Account is One to One you change grouping to Collectors.toMap(..)