java集合并交差

 

 public <T> Set<T> union(Set<T> a,Set<T> b){
        Set<T> objects = new HashSet<>(a);
        objects.addAll(b);
        return objects;
    }

    public <T> Set<T> intersection(Set<T> a,Set<T> b){
        Set<T> objects = new HashSet<>(a);
        objects.retainAll(b);
        return objects;
    }

    public <T> Set<T> diff(Set<T> a,Set<T> b){
        Set<T> objects = new HashSet<>(a);
        objects.removeAll(b);
        return objects;
    }