字符串合并处理

import java.util.*;

public class Main {

    private Map<Character, Character> map;

    public Main() {
        map = new HashMap<>();
        map.put('0', '0');
        map.put('1', '8');
        map.put('2', '4');
        map.put('3', 'C');
        map.put('4', '2');
        map.put('5', 'A');
        map.put('6', '6');
        map.put('7', 'E');
        map.put('8', '1');
        map.put('9', '9');
        map.put('a', '5');
        map.put('b', 'D');
        map.put('c', '3');
        map.put('d', 'B');
        map.put('e', '7');
        map.put('f', 'F');
        map.put('A', '5');
        map.put('B', 'D');
        map.put('C', '3');
        map.put('D', 'B');
        map.put('E', '7');
        map.put('F', 'F');
    }

    private String sort(String merge) {
        char[] even = new char[(merge.length() + 1) / 2];
        char[] odd  = new char[merge.length() / 2];
        for (int i = 0, j = 0; i < even.length; j += 2) {
            even[i++] = merge.charAt(j);
        }
        for (int i = 0, j = 1; i < odd.length; j += 2) {
            odd[i++] = merge.charAt(j);
        }
        Arrays.sort(even);
        Arrays.sort(odd);
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < even.length || i < odd.length; i++)  {
            if (i < even.length) {
                s.append(even[i]);
            }
            if (i < odd.length) {
                s.append(odd[i]);
            }
        }
        return s.toString();
    }

    // 找了好久，这里有坑，若字符不在map中，则保留原值
    private String transfer(String str)     {
        StringBuilder s = new StringBuilder();
        for (char ch : str.toCharArray()) {
            s.append(map.getOrDefault(ch, ch));
        }
        return s.toString();

    }

    public String processString(String str1, String str2) {
        String merge = sort(str1 + str2);
        String res = transfer(merge);
        return res;
    }

    public static void main(String[] args) {
        Main solution = new Main();
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            String str1 = in.next();
            String str2 = in.next();
            String res = solution.processString(str1, str2);
            System.out.println(res);
        }
    } 
}