Sorting an ArrayList based on a field?

Question

Hi I have an arrayList which has some objects.also my objects has two fields (1) name (2) cost I want to sort this arrayList with its cost field.is there any special method that do it for me or I should write it myself?also if there is some method for doeing this ,what is its time complexity(O(n),(O(nlogn))?

thanks

Answer 1

If you like type saftey (not using BeanComparator), then you need to write your own comparator.

eg

Collections.sort(list, new Comparator<SomeType>() {
    public int compareTo(SomeType lhs, SomeType rhs) {
        return lhs.getCost().compareTo(rhs.getCost());
    }
});

Note, this is not null safe (can cost be null?).

The other option would be to use BeanComparator, but make sure you add a test which makes sure that the sorting always works in case the method name changes.

Answer 2

如果为需要比较的对象实现Comparator接口，则可以使用Collections.sort()方法进行排序。

Answer 3

签出Bean Comparator几个选项。