如何将map的键连接到字符串中？

import java.util.HashMap;
import java.util.Map;

public class MapKeyToString {
    public static void main(String[] args) {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "Apple");
        map.put(2, "Banana");
        map.put(3, "Orange");

        StringBuilder sb = new StringBuilder();
        for (Integer key : map.keySet()) {
            sb.append(key.toString());
        }

        String result = sb.toString();
        System.out.println("连接后的字符串：" + result);
    }
}