java linkedlist copy : why my compiler show clone method error?

This is my code, in this line

 tem_left = (LinkedList) leftover.clone();

my Intellij showed red wave line under .clone() method (BTW, how to discribe this red wave line? hint error?) It says clone() has protected access in Java.lang.Object. This is what I found online that copy a Linkedlist to another one. What did i do wrong and how should I correct it?

package lc_771_Jewels;

import java.util.*;

import java.util.LinkedList;
import java.util.Queue;

public class Jewels_discuss {
    public int count_jewels(String jewels, String stones){
        char[] jewels_kind = jewels.toCharArray();
        char[] stone_list = stones.toCharArray();
        int count = 0;
        Queue<Character> tem_left = new LinkedList<>();
        for (int i = 0; i < stone_list.length; i++) {
           tem_left.offer(stone_list[i]);
        }
        for (int i = 0; i < jewels_kind.length; i++) {
            Queue<Character> leftover = new LinkedList<>();
            char tem_jewel = jewels_kind[i];
            for (int j = 0; j < tem_left.size(); j++) {
                if (tem_jewel!= stone_list[i]  ){
                    leftover.offer(stone_list[i]) ;
                }
                else {
                    count++;
                }
            }
            tem_left = (LinkedList) leftover.clone();
        }
        return count;
    }
}