import com.google.common.collect.Lists;
import lombok.Data;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Test {

    public static void main(String[] args) {
        TaskNode taskNode = new TaskNode();
        ArrayList<TaskNode> taskNodeList = Lists.newArrayList(taskNode);


        List<String> nodeStateList2 = taskNodeList.stream()
                .map(taskNode1 -> getString(taskNode1.getConfig(), ""))
                .collect(Collectors.toList());
    }

    public static <K> String getString(final Map<? super K, ?> map, final K key) {
        if (map != null) {
            final Object answer = map.get(key);
            if (answer != null) {
                return answer.toString();
            }
        }
        return null;
    }

}


@Data
class TaskNode{
    private LinkedHashMap config;
}

Unable to compile and On the console display: “java.lang.Object Unable to convert to
java.util.List<java.lang.String>”

I know it’s because the TaskNode.config property doesn’t declare generics, but I don’t understand why. Can you explain in detail the reasons for the occurrence