将Hashmap写入文件

import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.io.IOException;
import java.util.HashMap;

public class HashMapWriter {
    public static void main(String[] args) {
        HashMap<String, Integer> hashmap = new HashMap<>();
        hashmap.put("key1", 1);
        hashmap.put("key2", 2);
        hashmap.put("key3", 3);

        try {
            FileOutputStream fileOut = new FileOutputStream("hashmap.ser");
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            out.writeObject(hashmap);
            out.close();
            fileOut.close();
            System.out.println("Hashmap已写入文件");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.FileInputStream;
import java.io.ObjectInputStream;
import java.io.IOException;
import java.util.HashMap;

public class HashMapReader {
    public static void main(String[] args) {
        HashMap<String, Integer> hashmap = null;

        try {
            FileInputStream fileIn = new FileInputStream("hashmap.ser");
            ObjectInputStream in = new ObjectInputStream(fileIn);
            hashmap = (HashMap<String, Integer>) in.readObject();
            in.close();
            fileIn.close();
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }

        if (hashmap != null) {
            System.out.println("从文件中读取的Hashmap内容：");
            for (String key : hashmap.keySet()) {
                System.out.println(key + ": " + hashmap.get(key));
            }
        }
    }
}