package com.crland.ims.service.util;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * List中快速查詢物件
 * Author: Ping.Chen
 * @Date: 2018/6/15 15:30
 */
public class FSearchUtil {
    private StringBuffer mKeyWordString = new StringBuffer();
    private List<Object> mSearchObjs = new ArrayList<>();
    private int[] mIndexes;

    public FSearchUtil(List<? extends Object> objects, String... fields) throws Exception {
        super();
        init(objects, fields);
    }

    private void init(List<? extends Object> objs, String... fields) throws Exception {
        if (objs != null) {
            mKeyWordString.setLength(0);
            mSearchObjs.clear();
            mSearchObjs = new ArrayList<>(objs);
            mIndexes = new int[mSearchObjs.size() * 2];
            int index = 0;
            for (int i = 0; i < mSearchObjs.size(); i++) {
                Object info = mSearchObjs.get(i);
                // 指定要搜尋的欄位
                String searchKey = getSearchKey(info, fields);
                // 將該字串在總字串中的起終位置儲存下來,位置是索引值而非長度
                int length = mKeyWordString.length();
                mIndexes[index] = length;
                mKeyWordString.append(searchKey);
                length = mKeyWordString.length();
                index++;
                // 儲存新加搜尋欄位的索引值
                mIndexes[index] = (length > 0) ? length - 1 : 0;
                index++;
            }
        }
    }

    /**
     * 通過反射從物件中取出指定欄位的值
     */
    private String getSearchKey(Object obj, String... fields) throws Exception {
        StringBuilder searchKeys = new StringBuilder();
        Class<? extends Object> clazz = obj.getClass();
        try {
            for (String str : fields) {
                // 搜尋欄位使用空格隔開
                Field f = clazz.getDeclaredField(str);
                f.setAccessible(true);
                Object val = f.get(obj);
                searchKeys.append(val).append(" ");
                f.setAccessible(false);
            }
        } catch (Exception e) {
            throw new Exception("取值異常：" + e.getMessage());
        }
        return searchKeys.toString();
    }

    /**
     * 搜尋結果
     *
     * @param keyWords
     *            搜尋的關鍵字，要去掉首尾的空格
     * @return 返回搜尋到的物件
     */
    public List<Object> searchTasks(String keyWords) {
        List<Object> searchedTask = new ArrayList<>();
        int[] searchIndex = getSearchIndex(keyWords);
        for (int index : searchIndex) {
            if (index != -1 && index < mSearchObjs.size() * 2) {
                Object info = mSearchObjs.get(index / 2);
                if (info != null && !searchedTask.contains(info)) {
                    searchedTask.add(info);
                }
            }
        }
        return searchedTask;
    }

    /**
     * 找到匹配的索引資料
     *
     * @param keyWords
     *            搜尋的關鍵字
     * @return 在初始化的索引陣列的下標陣列
     */
    private int[] getSearchIndex(String keyWords) {
        Pattern pattern = Pattern.compile(keyWords, Pattern.CASE_INSENSITIVE | Pattern.LITERAL);
        Matcher matcher = pattern.matcher(mKeyWordString.toString());
        ArrayList<Integer> searchResult = new ArrayList<>();
        while (matcher.find()) {
            // 不宜在此處再做迴圈，否則可能造成迴圈次數過多錯誤
            searchResult.add(matcher.start());
        }
        int[] searchIndexes = new int[searchResult.size()];
        for (int i = 0; i < searchIndexes.length; i++) {
            int findIndex = findIndex(searchResult.get(i));
            searchIndexes[i] = (findIndex / 2) * 2;
        }
        return searchIndexes;
    }

    /**
     * 使用二分法找到指定字元位置在索引陣列中的位置
     *
     * @param charAt
     *            字元在整個字串中的位置
     * @return 在索引陣列中的位置
     */
    private int findIndex(int charAt) {
        int low = 0;
        int high = mIndexes.length - 1;
        int mid = -1;
        while (low <= high) {
            mid = (low + high) >>> 1;
            int midVal = mIndexes[mid];
            if (midVal < charAt) {
                low = mid + 1;
            } else if (midVal > charAt) {
                high = mid - 1;
            } else {
                return mid;
            }
        }
        return mid;
    }
}
 

使用：

FSearchUtil tool = new FSearchUtil(points, "id");
List<LandPoint> landPointList = (List<LandPoint>) (List) tool.searchTasks(100); //強轉