java - 从字符串表达式(ArrayList 到 Array)存储 First Case 变量

Question

我正在努力将变量的第一个案例存储到数组中，因为我不知道会有多少个变量，所以我决定使用数组列表。

编译时出现以下错误:

javac TruthTester.java
TruthTester.java:102: error: no suitable method found for toArray(char[])
char[] charArr = letters.toArray(x);
^
method ArrayList.<T>toArray(T[]) is not applicable
(inferred type does not conform to declared bound(s)
inferred: char bound(s): Object)
method ArrayList.toArray() is not applicable
(actual and formal argument lists differ in length)
where T is a type-variable:
T extends Object declared in method <T>toArray(T[])
1 error

这是我的代码段..

private static char[] getVariables(String[] lines)
{
    ArrayList<Character> letters = new ArrayList<Character>();

    int count = 0;
    for(int x = 0; x < lines.length; x++)
    {
        for(int i = 0; i < lines[x].length(); i++)
        {
            char tempStore = 'a';
            boolean isCopy = false;
            int counter = 0;
            for(char letter : letters)
            {
                if(isAlphabeticToken(letter)){
                    if(lines[x].charAt(counter) == letter)
                    {
                        isCopy = true;
                    }
                    else
                    {
                        isCopy = false;
                        tempStore = letter;
                    }
                }
                else
                {
                    isCopy = true;
                }
                counter++;
            }
            if(!isCopy)
            {
                letters.add(tempStore);
                count++;
            }
        }
    }
            /*
             * ==========
             * ERROR HERE
             * ==========
             */
    char[] x = new char[letters.size()];
    char[] charArr = letters.toArray(x);

    return charArr;
}

Answer 1

你无法获得 char[]从一个ArrayList<Character> , 你只能得到一个 Character[] ，装箱/拆箱不会使它们等同。

您是否考虑过使用 StringBuilder反而？这实际上是专门为保存可变的、未知长度的字符组而设计的。