如何在Java中为Map创建唯一的id？

import java.util.UUID;
import java.util.Map;

public class UniqueIdGenerator {
    public static void main(String[] args) {
        Map<String, Object> map = new HashMap<>();
        String id = UUID.randomUUID().toString();
        map.put(id, "value");
        System.out.println("Map id: " + id);
    }
}

import java.util.concurrent.atomic.AtomicLong;
import java.util.Map;

public class UniqueIdGenerator {
    private static AtomicLong counter = new AtomicLong(0);

    public static void main(String[] args) {
        Map<Long, Object> map = new HashMap<>();
        long id = counter.incrementAndGet();
        map.put(id, "value");
        System.out.println("Map id: " + id);
    }
}