map转string与string转map

public static String mapToString(Map<String,String> map){
        //获取所有map集合的key
        Set<String> keySet = map.keySet();
        //将set集合转换为数组
        String[] arr = keySet.toArray(new String[keySet.size()]);
        //给数组排序（升序）
        Arrays.sort(arr);
        //拼接
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < arr.length; i++) {
            if(map.get(arr[i]).trim().length()>0){
                sb.append(arr[i]).append("=").append(map.get(arr[i]).trim());
            }
            if(i != arr.length-1){
                sb.append("&");
            }
        }
        return sb.toString();
    }

    public static Map<String,String> stringToMap(String str){
        if(null == str || "".equals(str)){
            return null;
        }

        String[] arr = str.split("&");

        //设置hashMap的长度
        int length = arr.length % 2 == 0 ? arr.length : arr.length + 1;

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

        for (int i = 0; i < arr.length; i++) {
            String[] keyValue = arr[i].split("=");
            map.put(keyValue[0],keyValue[1]);
        }
        return map;
    }