Java 在函数之间压缩字符串

我正在开发一个程序，该程序将获取一个文本文件，并将数字从0-99转换为单词（即0->“零”，99->“九十九”）。我能够在一个函数中转换数字并将其附加到字符串中，但最终的sting输出不包含任何转换后的数字。代码如下：

static ArrayList<String> list;

    static void convertToWord(char[] num, String fullString)
    {
        //number to word : https://www.geeksforgeeks.org/convert-number-to-words/
        String[] single_digits = new String[]{ "zero", "one",
                "two", "three", "four",
                "five", "six", "seven",
                "eight", "nine"};
        String[] two_digits = new String[]{"", "ten", "eleven", "twelve",
                "thirteen", "fourteen",
                "fifteen", "sixteen", "seventeen",
                "eighteen", "nineteen"};
        String[] tens_multiple = new String[]{"", "", "twenty", "thirty", "forty",
                "fifty","sixty", "seventy",
                "eighty", "ninety"};

        int len = num.length;

        if (len == 0)
        {
            System.out.println("Error");
            return;
        }

        if (len == 1)
        {
            fullString += single_digits[num[0] - '0'];
            return;
        }

        if (len > 2)
        {
            System.out.println("No numbers greater than 99");
            return;
        }

        int x = 0;
        while (x < num.length)
        {
                if (num[x] - '0' == 1)
                {
                    int sum = num[x] - '0' +
                            num[x] - '0';
                    fullString += two_digits[sum];
                    return;
                }

                else if (num[x] - '0' == 2 &&
                        num[x + 1] - '0' == 0)
                {
                    fullString += "twenty";
                    return;
                }

                else
                {
                    int i = (num[x] - '0');
                    if(i > 0)
                        fullString += tens_multiple[i]+" ";
                    else
                        fullString += "";
                    ++x;
                    if (num[x] - '0' != 0)
                        fullString += single_digits[num[x] - '0'];
                }
            ++x;
        }
    System.out.println(fullString);
    }

    public static void main(String[] args) throws FileNotFoundException
    {
        /* read each element of file as a separate member of array:
        https://stackoverflow.com/questions/28643680/java-storing-each-word-from-an-input-file-in-an-array-of-strings */
        String fullString = "";
        Scanner s = new Scanner(new File("C:/Users/Zach/Desktop/Fall 2020/Java_Kotlin/java-kotlin-zpheesaker/KattisNumberstoWords/app/input.txt"));
        list = new ArrayList<String>();
        while(s.hasNext())
        {
            String token = s.next ();
            list.add(token);
        }

        for (int i = 0; i < list.size(); i++)
        {
            // check if number by regex: https://stackoverflow.com/questions/18590901/check-if-a-string-contains-numbers-java
            if(list.get(i).matches(".*\\d.*"))
            {
                convertToWord(list.get(i).toCharArray(), fullString);
            }
            else {
                fullString += (list.get(i) + " ");
            }
        }
        System.out.println(fullString);
    }
}

以下是输入文件中的三行：

Piqued favour 23 stairs it enable exeter as seeing.
Remainder met improving but 41 engrossed sincerity age.
Better but 78 length denied abroad are.

---

正如您所看到的，该数字在函数convertToWord中随system.out一起追加和打印，但一旦返回main，该数字就会丢失。如何跨函数将这些转换附加到字符串中？

我可以想出两种方法：

如果要将

fullString

的值返回到

main

方法，我建议您修改

convertToWord

，使其具有返回类型

String

，如下所示：

static void convertToWord(char[] num, String fullString)

然后，该方法需要返回fullString，而不是什么也不返回

最后，将main方法中的返回值或convertToWord指定给一个变量，您可以在

main

中使用它

或者，您可以将fullString声明为

StringBuffer

，并使用方法

append（）

对其进行追加

static void convertToWord(char[] num, String fullString)