在ArrayList中查找和修改特定元素

Question

is some elegant way to find and modify some specific object in java? I have method like that:

public update(MyObj o) {
   for (MyObj objToModify: DATA) {
       if (objToModify.getId() == o.getId()) {
           objToModify.setName(o.getName());
           // and so on ...
       }
   }
}

Is possible to rewrite to lambda for example, or some other feature of Java 8? I had a lot of properties so I will prefer some option where I couldn't write manually set up all of new properties.

Answer 1

You can do it in the following way, this will go over the whole stream and update elements even if there is more then one matching:

DATA.stream().filter(a -> a.getId() == o.getId()).forEach(a -> a.setName(o.getName()));

Or if you are sure that you only need to update one element:

DATA.stream().filter(a -> a.getId() == o.getId()).
    findAny().ifPresent(a -> a.setName(o.getName()));

Both solutions will throw NullPointerException if DATA has null elements the same as your original solution, if it's a posiibility and you want to prevent it you need to also check that a is not null in filter .

Answer 2

You can use lambda expression to do what you are trying to do

public update(MyObj o) {

    DATA.forEach(objToModify -> {

        if (objToModify.getId() == o.getId()) {
            objToModify.setName(o.getName());
            // and so on ...
        }
    });   
}

although i am not sure if using lambda expression in your case will be more efficient than using for-each loop.