ArrayList<HashMap<String, String>> grpList2 的转化成Object类型

ArrayList<HashMap<String, String>> grpList2 可以通过序列化（Serialization）来转换成 Object 类型。具体实现方法可以使用 Java 自带的序列化类 ObjectInputStream 和 ObjectOutputStream。示例代码如下：

import java.io.*;
import java.util.ArrayList;
import java.util.HashMap;

public class SerializeDemo {

    public static void main(String[] args) {

        ArrayList<HashMap<String, String>> grpList2 = new ArrayList<>();
        HashMap<String, String> map1 = new HashMap<>();
        map1.put("key1_1", "value1_1");
        map1.put("key1_2", "value1_2");
        HashMap<String, String> map2 = new HashMap<>();
        map2.put("key2_1", "value2_1");
        map2.put("key2_2", "value2_2");
        grpList2.add(map1);
        grpList2.add(map2);

        // 将 ArrayList<HashMap<String, String>> 转换成 Object 类型
        try {
            FileOutputStream fileOut = new FileOutputStream("grpList2.ser");
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            out.writeObject(grpList2);
            out.close();
            fileOut.close();
            System.out.println("Serialized data is saved in grpList2.ser");
        } catch (IOException i) {
            i.printStackTrace();
        }

        // 从 Object 类型转换回 ArrayList<HashMap<String, String>>
        try {
            FileInputStream fileIn = new FileInputStream("grpList2.ser");
            ObjectInputStream in = new ObjectInputStream(fileIn);
            ArrayList<HashMap<String, String>> grpList2FromSer = (ArrayList<HashMap<String, String>>) in.readObject();
            in.close();
            fileIn.close();

            System.out.println("Deserialized data:");
            System.out.println(grpList2FromSer.get(0).get("key1_1"));
            System.out.println(grpList2FromSer.get(0).get("key1_2"));
            System.out.println(grpList2FromSer.get(1).get("key2_1"));
            System.out.println(grpList2FromSer.get(1).get("key2_2"));

        } catch (IOException i) {
            i.printStackTrace();
            return;
        } catch (ClassNotFoundException c) {
            System.out.println("ArrayList<HashMap<String, String>> class not found");
            c.printStackTrace();
            return;
        }
    }
}

输出结果为：

Serialized data is saved in grpList2.ser
Deserialized data:
value1_1
value1_2
value2_1
value2_2