一个Java list 里面有多个数据对象，其中有一个字段是“grounding_state”，我仅需要从list里面取一条数据,根据“grounding_state”的值取数据的顺序为1>2>0>3>5，怎么实现

可以先定义一个根据“grounding_state”值排序的比较器类，然后使用Collections.sort()方法对list进行排序，最后取出第一个元素即可。

以下是示例代码：

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<DataObject> list = new ArrayList<>();
        list.add(new DataObject(2));
        list.add(new DataObject(3));
        list.add(new DataObject(1));
        list.add(new DataObject(0));
        list.add(new DataObject(5));

        Collections.sort(list, new GroundingStateComparator());
        DataObject result = list.get(0);
        System.out.println(result.toString());
    }

    static class DataObject {
        int groundingState;

        public DataObject(int groundingState) {
            this.groundingState = groundingState;
        }

        public int getGroundingState() {
            return groundingState;
        }

        @Override
        public String toString() {
            return "DataObject{" +
                    "groundingState=" + groundingState +
                    '}';
        }
    }

    static class GroundingStateComparator implements Comparator<DataObject> {
        private final int[] order = {1, 2, 0, 3, 5};

        @Override
        public int compare(DataObject o1, DataObject o2) {
            int index1 = getIndex(o1.getGroundingState());
            int index2 = getIndex(o2.getGroundingState());
            return Integer.compare(index1, index2);
        }

        private int getIndex(int groundingState) {
            for (int i = 0; i < order.length; i++) {
                if (groundingState == order[i]) {
                    return i;
                }
            }
            return order.length;
        }
    }
}

输出结果为：

DataObject{groundingState=1}