检查2组并获取所有已删除/添加的表单/到第一组元素

Question

I have 2 Sets and I need equals this sets and get removed and added elements. I do it

public static void main(String[] args) {
        System.out.println("start");
        Set<String> setDestOrigin = new HashSet<>();
        Set<String> setLocalOrigin = new HashSet<>();

        setDestOrigin.add("test1");
        setDestOrigin.add("test2");
        setDestOrigin.add("test3");
        setDestOrigin.add("test7");
        setDestOrigin.add("test5");

        setLocalOrigin.add("test1");
        setLocalOrigin.add("test2");
        setLocalOrigin.add("test3");
        setLocalOrigin.add("test4");
        setLocalOrigin.add("test5");


        Set<String> deleted = new HashSet<>(setLocalOrigin);
        deleted.removeAll(setDestOrigin);

        Set<String> added = new HashSet<>(setDestOrigin);
        added.removeAll(setLocalOrigin);

        System.out.println("finish");
    }

In deleted set I have all element each was removed from setDestOrigin In added set I have all element each was added to setDestOrigin

Is there a way to do the same thing easier?

Answer 1

Your approach looks like correct one. You also could try Guava's Sets.difference(set1, set2). It returns an unmodifiable view which implements Set interface.

Answer 2

If you have Guava, you can use Sets.difference() , which returns a view of the difference between two sets. This can be more efficient than copying and removing elements. They also have convenient utilities for initializing collections:

Set<String> setDestOrigin = ImmutableSet.of("test1", "test2", "test3", "test7", "test5");
Set<String> setLocalOrigin = ImmutableSet.of("test1", "test2", "test3", "test4", "test5");

Set<String> deleted = Sets.difference(setLocalOrigin, setDestOrigin);
Set<String> added = Sets.difference(setDestOrigin, setLocalOrigin);