如何使用Java从JSON文件中获取密钥数？

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.JsonNode;

import java.io.File;
import java.io.IOException;

public class JsonKeyReader {
    public static void main(String[] args) {
        try {
            // 读取JSON文件
            File jsonFile = new File("path/to/json/file.json");
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode rootNode = objectMapper.readTree(jsonFile);

            // 获取密钥数
            int keyCount = rootNode.get("keys").size();

            System.out.println("密钥数：" + keyCount);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

{
  "keys": [
    "key1",
    "key2",
    "key3"
  ]
}