我应该在成员变量中存储对map的引用吗？

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class MyClass {
    // 实例变量
    private Map<String, String> instanceMap = new HashMap<>();

    // 静态变量
    private static Map<String, String> staticMap = new ConcurrentHashMap<>();

    public void addToInstanceMap(String key, String value) {
        instanceMap.put(key, value);
    }

    public String getFromInstanceMap(String key) {
        return instanceMap.get(key);
    }

    public static void addToStaticMap(String key, String value) {
        staticMap.put(key, value);
    }

    public static String getFromStaticMap(String key) {
        return staticMap.get(key);
    }
}