排序Java集合

Question

我有一个Java集合：

Collection<CustomObject> list = new ArrayList<CustomObject>();

CustomObject id现在在显示列表之前有一个字段，我想按此排序此集合id。

有什么办法可以做到吗？

Answer 1

使用比较器：

List<CustomObject> list = new ArrayList<CustomObject>();
Comparator<CustomObject> comparator = new Comparator<CustomObject>() {
    @Override
    public int compare(CustomObject left, CustomObject right) {
        return left.getId() - right.getId(); // use your logic
    }
};

Collections.sort(list, comparator); // use the comparator as much as u want
System.out.println(list);

此外，如果CustomObject实现Comparable，则只需使用Collections.sort(list)

使用JDK 8，语法要简单得多。

List<CustomObject> list = getCustomObjectList();
Collections.sort(list, (left, right) -> left.getId() - right.getId());
System.out.println(list);

更简单

List<CustomObject> list = getCustomObjectList(); list.sort((left, right) -> left.getId() - right.getId()); System.out.println(list);

最简单的

List<CustomObject> list = getCustomObjectList();
list.sort(Comparator.comparing(CustomObject::getId));
System.out.println(list);

显然，初始代码也可以用于JDK 8。