Andr运行程序后闪退

package com.example.endtext;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity {
    private List<Map<String,Object>> list=new ArrayList<>();
    private RecyclerView recyclerView;
    private Adapter adapter;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        adapter=new Adapter(MainActivity.this,list);
        recyclerView=findViewById(R.id.recycler);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(adapter);




    Thread thread=new Thread(new Runnable() {
        @Override
        public void run() {
            HttpURLConnection connection=null;
            BufferedReader reader=null;
            try {
                URL url=new URL("http://news-at.zhihu.com/api/3/stories/latest");
                connection= (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("GET");
                connection.setConnectTimeout(8000);
                connection.setReadTimeout(8000);
                InputStream in=connection.getInputStream();
                reader=new BufferedReader(new InputStreamReader(in));
                StringBuilder response=new StringBuilder();
                String line;
                while ((line=reader.readLine())!=null){
                    response.append(line);
                }
                showResponse(response.toString());
            } catch (IOException e) {
                e.printStackTrace();
                AlertDialog textTips1 = new AlertDialog.Builder(MainActivity.this)
                        .setTitle("Tips:")
                        .setMessage("。\n")
                        .create();
                textTips1.show();
            }finally {
                if(reader!=null){
                    try {
                        reader.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                        AlertDialog textTips2 = new AlertDialog.Builder(MainActivity.this)
                                .setTitle("Tips:")
                                .setMessage("1\n")
                                .create();
                        textTips2.show();
                    }
                }
            }
        }
    });thread.start();}
        private void showResponse(String string) {


            try {
                JSONObject jsonObject = new JSONObject(string);
                JSONArray jsonArray =new JSONArray(jsonObject.getJSONObject("stories"));
                for (int i=0;i<jsonArray.length();i++){
                    JSONObject jsonObject1 = jsonArray.getJSONObject(i);
                    String title = jsonObject1.getString("title");
                    Map<String,Object> map=new HashMap<>();
                    map.put("title", title);
                    list.add(map); }

                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {

                    }
                });

            } catch (JSONException e) {
                e.printStackTrace();
                AlertDialog textTips3 = new AlertDialog.Builder(MainActivity.this)
                        .setTitle("Tips:")
                        .setMessage("圆\n")
                        .create();
                textTips3.show();
            }
        }
}