注意：配合ExcelHelper帮助类使用

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.stream.Collectors;

public class ListHelper {

	/**
	 * 判断excel是否重复数据 是true 否false
	 * 
	 * @param excelFileName
	 * @param args
	 * @return
	 */
	public static boolean isExcelRepeat(String excelFileName, int... args) {
		try {
			ArrayList<ArrayList<String>> arr = ExcelHelper.getExcel(excelFileName, args);
			int oldRow = arr.size();
			int newRow = removeRepeatLow(arr).size();
			// int newRow1 = removeRepeatHeight(arr).size();
			if (oldRow != newRow) {
				return true;
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return false;
	}

	/**
	 * 去除重复数据低版本jdk
	 * 
	 * @param list
	 * @return
	 */
	public static ArrayList<ArrayList<String>> removeRepeatLow(ArrayList<ArrayList<String>> list) {
		HashSet hs = new HashSet(list);
		list.clear();
		list.addAll(hs);
		return list;
	}

	/**
	 * 去除重复数据高版本jdk
	 * 
	 * @param list
	 * @return
	 */
	public static ArrayList<ArrayList<String>> removeRepeatHeight(ArrayList<ArrayList<String>> list) {
		ArrayList<ArrayList<String>> arr = (ArrayList<ArrayList<String>>) list.stream().distinct()
				.collect(Collectors.toList());
		return arr;
	}

	/**
	 * list分页
	 * 
	 * @param list
	 * @param pageSize
	 * @return
	 */
	public static <T> List<List<T>> splitList(List<T> list, int pageSize) {

		int listSize = list.size();
		int page = (listSize + (pageSize - 1)) / pageSize;

		List<List<T>> listArray = new ArrayList<List<T>>();
		for (int i = 0; i < page; i++) {
			List<T> subList = new ArrayList<T>();
			for (int j = 0; j < listSize; j++) {
				int pageIndex = ((j + 1) + (pageSize - 1)) / pageSize;
				if (pageIndex == (i + 1)) {
					subList.add(list.get(j));
				}
				if ((j + 1) == ((j + 1) * pageSize)) {
					break;
				}
			}
			listArray.add(subList);
		}
		return listArray;
	}

	/**
	 * list1.addAll(list2); //并集
	 * 
	 * list2.removeAll(list1);list1.addAll(list2); //去重复并集
	 * 
	 * list1.retainAll(list2); //交集
	 * 
	 * list1.removeAll(list2); //差集
	 */
}

原文链接：https://www.idaobin.com/archives/2058.html

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