去除Map中的null 改为““

import java.util.Map;
import java.util.Set;

public class MapUtil  {
    
    public static Map nullToEmpty(Map map) {
        Set set = map.keySet();
        if (set != null && !set.isEmpty()) {
            for (String key : set) {
                if (map.get(key) == null) {
                    map.put(key, "");
                }
            }
        }
        return map;
    }
}