从文本文件读取时如何获取char[]的大小

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileCharSize {
    public static void main(String[] args) {
        String filePath = "path/to/textfile.txt";
        char[] content = readTextFile(filePath);
        int charSize = content.length;
        System.out.println("Char[] size: " + charSize);
    }

    private static char[] readTextFile(String filePath) {
        StringBuilder sb = new StringBuilder();
        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
            String line;
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sb.toString().toCharArray();
    }
}