java对两个字符串数组取交集、并集和差集

import java.util.*;

public class StringArrayUtil {
    // 求两个字符串数组的并集，利用set的元素唯一性
    public static String[] union(String[] arr1, String[] arr2) {
        Set set = new HashSet();
        Collections.addAll(set, arr1);
        Collections.addAll(set, arr2);
        
        String[] result = {};
        return set.toArray(result);
    }

    // 求两个数组的交集
    public static String[] intersect(String[] arr1, String[] arr2) {
        Map map = new HashMap();
        LinkedList list = new LinkedList();
        for (String str : arr1) {
            if (!map.containsKey(str)) {
                map.put(str, Boolean.FALSE);
            }
        }
        for (String str : arr2) {
            if (map.containsKey(str)) {
                map.put(str, Boolean.TRUE);
            }
        }

        for (Map.Entry e : map.entrySet()) {
            if (e.getValue().equals(Boolean.TRUE)) {
                list.add(e.getKey());
            }
        }

        String[] result = {};
        return list.toArray(result);
    }

    // 求两个数组的差集
    public static String[] minus(String[] arr1, String[] arr2) {
        LinkedList list = new LinkedList();
        LinkedList history = new LinkedList();
        String[] longerArr = arr1;
        String[] shorterArr = arr2;
        // 找出较长的数组来减较短的数组
        if (arr1.length > arr2.length) {
            longerArr = arr2;
            shorterArr = arr1;
        }
        for (String str : longerArr) {
            if (!list.contains(str)) {
                list.add(str);
            }
        }
        for (String str : shorterArr) {
            if (list.contains(str)) {
                history.add(str);
                list.remove(str);
            } else {
                if (!history.contains(str)) {
                    list.add(str);
                }
            }
        }

        String[] result = {};
        return list.toArray(result);
    }
}