Android Studio'da Projedeki Kod Hatası Nasıl Düzeltilir?

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
 Button giris, kaydol;
 EditText email, parola;
 public static ArrayList<uye> uyeler = new ArrayList<uye>();

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 giris = findViewById(R.id.button);
 kaydol = findViewById(R.id.button2);
 email= findViewById(R.id.editTextPersonName31);
 parola= findViewById(R.id.editTextPassword);
 giris.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View view) {
 boolean kontrol = false;
 for (int i = 0; i <uyeler.size(); i++) {
 if (uyeler.get(i).eposta.equals(email.getText().toString()) &&
 uyeler.get(i).sifre.equals(parola.getText().toString())) {
 kontrol = true;
 break;
 }
 }
 if (kontrol==true) {
 Intent grsyap = new Intent(MainActivity.this, bilgiler.class);
 startActivity(grsyap);
 } else {
 Toast.makeText(MainActivity.this, "Hatalı", Toast.LENGTH_SHORT).show();
 }
 kaydol.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View view) {
 Intent gidis = new Intent(MainActivity.this, kayitsayfa.class);
 startActivity(gidis);
 }
 });
 }
 });
 }
}

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import java.util.ArrayList;

public class kayitsayfa extends AppCompatActivity {
 Button kydl, geri;
 EditText kad, soy, ke, ks;
 public static ArrayList<uye> uyeler = new ArrayList<uye>();

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_kayitsayfa);
 kydl = findViewById(R.id.button3);
 geri = findViewById(R.id.button4);
 kad = findViewById(R.id.editTextTextPersonName2);
 soy = findViewById(R.id.editTextTextPersonName3);
 ke = findViewById(R.id.editTextTextPersonName4);
 ks = findViewById(R.id.editTextTextPassword2);
 geri.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View view) {
 Intent don = new Intent(kayitsayfa.this, MainActivity.class);
 startActivity(don);
 }
 });
 kydl.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View view) {
 boolean varmi = false;
 for (int i = 0; i < uyeler.size(); i++) {
 if (ke.getText().toString().equals(uyeler.get(i).eposta)) {
 varmi = true;
 Toast.makeText(kayitsayfa.this, "Bu Hesap Zaten Kayıtlı", Toast.LENGTH_SHORT).show();
 break;
 }
 }
 if (varmi == false) {
 uyeler.add(new uye(kad.getText().toString(),
 soy.getText().toString(),
 ke.getText().toString(),
 ks.getText().toString()));
 Toast.makeText(kayitsayfa.this, "Başarıyla kaydolundu", Toast.LENGTH_SHORT).show();

 }
 }
 });

 }