java实现列表的上下移动和置顶操作

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wx5a8fb619345a4 2021-07-12 10:29:37

文章标签 Java 文章分类 Java 后端开发

3) controller

@RequestMapping(value = "/courseSortUpdate",method = RequestMethod.GET,produces = {"text/html;charset=UTF-8"})
    public String courseSortUpdate(HttpServletRequest request){
        String sort=request.getParameter("sort");
        String sort1=sort.substring(0,6);
        WExcellentCourseEntity entity=courseService.infoBySort(sort1);
        if(sort.substring(sort.length()-1).equals("1")){
            WExcellentCourseEntity entity1=courseService.sortUp(sort1);           courseService.updateBySort(entity1.getSort(),entity.getId());
            courseService.updateBySort(Integer.parseInt(sort1),entity1.getId());
        }
        if(sort.substring(sort.length()-1).equals("2")){
            WExcellentCourseEntity entity2=courseService.sortDown(sort1);
            courseService.updateBySort(entity2.getSort(),entity.getId());
            courseService.updateBySort(Integer.parseInt(sort1),entity2.getId());
        }
        return "operation/ecList";
    }

二、列表中某行的置顶操作
1、思路依然是sort值的交换，只是除了普通的交换之外，还需要list的Collections.swap()方法。
2、如下是一个简单的demo：

public class stringTest {

    public static void main (String[] args){
        List<userTest> list=new ArrayList<>();
        userTest u1=new userTest();
        u1.setId(1);
        u1.setName("a");
        u1.setSort(1);
        userTest u2=new userTest();
        u2.setId(2);
        u2.setName("b");
        u2.setSort(2);
        userTest u3=new userTest();
        u3.setId(3);
        u3.setName("c");
        u3.setSort(3);
        userTest u4=new userTest();
        u4.setId(4);
        u4.setName("d");
        u4.setSort(4);
        userTest u5=new userTest();
        u5.setId(5);
        u5.setName("e");
        u5.setSort(5);
        userTest u6=new userTest();
        u6.setId(6);
        u6.setName("f");
        u6.setSort(6);
        userTest u7=new userTest();
        u7.setId(7);
        u7.setName("g");
        u7.setSort(7);

        list.add(u1);
        list.add(u2);
        list.add(u3);
        list.add(u4);
        list.add(u5);
        list.add(u6);
        list.add(u7);


        //1、交换list的0号数据和6号数据
        swap2(list, 6, 0);
        for (userTest e : list) {
            System.out.println(e.getId()+" "+e.getName() + " "+e.getSort()+" ");
        }
        System.out.println("-------------");
        //2、依次交换sort数据
        for(int i=0;i<list.size()-1;i++){
            int sort=list.get(i+1).getSort();
            list.get(i+1).setSort(list.get(i).getSort());
            list.get(i).setSort(sort);
        }
        for (userTest e : list) {
            System.out.println(e.getId()+" "+e.getName() + " "+e.getSort()+" ");
        }
    }

    public static <T> void swap2(List<T> list, int oldPosition, int newPosition) {
        if (null == list) {
            throw new IllegalStateException("The list can not be empty...");
        }
        if (oldPosition > newPosition) {
            for (int i = oldPosition; i > newPosition; i--) {
                Collections.swap(list, i, i - 1);
            }
        }
    }
}