import java.util.HashMap;

import java.util.HashSet;

import java.util.LinkedList;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Set;   

public class StringArray {

    public static void main(String[] args) {

        //测试union

        String[] arr1 = {"abc", "df", "abc"};

        String[] arr2 = {"abc", "cc", "df", "d", "abc"};

        String[] result_union = union(arr1, arr2);

        System.out.println("求并集的结果如下：");

        for (String str : result_union) {

            System.out.println(str);

        }

        //测试insect

        String[] result_insect = intersect(arr1, arr2);

        System.out.println("求交集的结果如下：");

        for (String str : result_insect) {

            System.out.println(str);

        }

          //测试minus

        String[] result_minus = minus(arr1, arr2);

        System.out.println("求差集的结果如下：");

        for (String str : result_minus) {

            System.out.println(str);

        }

    }

    //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<String> set = new HashSet<String>();

        for (String str : arr1) {

            set.add(str);

        }

        for (String str : arr2) {

            set.add(str);

        }

        String[] result = {};

        return set.toArray(result);

    }

    //求两个数组的交集

    public static String[] intersect(String[] arr1, String[] arr2) {

        Map<String, Boolean> map = new HashMap<String, Boolean>();

        LinkedList<String> list = new LinkedList<String>();

        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 (Entry<String, Boolean> 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<String> list = new LinkedList<String>();

        LinkedList<String> history = new LinkedList<String>();

        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);

    }

}