How to read all contacts in android?

This example demonstrate about How to read all contacts in android
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
Step 2 − Add the following code to res/layout/activity_main.xml.
<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
   android:layout_width = "match_parent"
   android:gravity = "center"
   android:layout_height = "match_parent">
   <ListView
      android:id = "@+id/list"
      android:layout_width = "wrap_content"
      android:textSize = "30sp"
      android:layout_height = "wrap_content"
      android:text = "Click"/>
</LinearLayout>
In the above code, we have taken list view.
Step 3 − Add the following code to src/MainActivity.java
<?xml version = "1.0" encoding = "utf-8"?>
import android.annotation.TargetApi;
import android.content.ContentResolver;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.os.Build;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
   public static final int REQUEST_READ_CONTACTS = 79;
   ListView list;
   ArrayList mobileArray;
   @TargetApi(Build.VERSION_CODES.LOLLIPOP)
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.READ_CONTACTS)
         == PackageManager.PERMISSION_GRANTED) {
         mobileArray = getAllContacts();
      } else {
         requestPermission();
      }
      list = findViewById(R.id.list);
      ArrayAdapter adapter = new ArrayAdapter<String>(this,
      android.R.layout.simple_list_item_1, android.R.id.text1, mobileArray);
      list.setAdapter(adapter);
   }
   private void requestPermission() {
      if (ActivityCompat.shouldShowRequestPermissionRationale(this, android.Manifest.permission.READ_CONTACTS)) {
         // show UI part if you want here to show some rationale !!!
      } else {
         ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.READ_CONTACTS},
         REQUEST_READ_CONTACTS);
      }
      if (ActivityCompat.shouldShowRequestPermissionRationale(this, android.Manifest.permission.READ_CONTACTS)) {
      } else {
         ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.READ_CONTACTS},
         REQUEST_READ_CONTACTS);
      }
   }
   @Override
   public void onRequestPermissionsResult(int requestCode,
   String permissions[], int[] grantResults) {
      switch (requestCode) {
         case REQUEST_READ_CONTACTS: {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
               mobileArray = getAllContacts();
            } else {
               // permission denied,Disable the
               // functionality that depends on this permission.
            }
            return;
         }
      }
   }
   private ArrayList getAllContacts() {
      ArrayList<String> nameList = new ArrayList<>();
      ContentResolver cr = getContentResolver();
      Cursor cur = cr.query(ContactsContract.Contacts.CONTENT_URI,
      null, null, null, null);
      if ((cur ! = null ? cur.getCount() : 0) > 0) {
         while (cur ! = null && cur.moveToNext()) {
            String id = cur.getString(
            cur.getColumnIndex(ContactsContract.Contacts._ID));
            String name = cur.getString(cur.getColumnIndex(
            ContactsContract.Contacts.DISPLAY_NAME));
            nameList.add(name);
            if (cur.getInt(cur.getColumnIndex( ContactsContract.Contacts.HAS_PHONE_NUMBER)) > 0) {
               Cursor pCur = cr.query(
               ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
               null,
               ContactsContract.CommonDataKinds.Phone.CONTACT_ID + " = ?",
               new String[]{id}, null);
               while (pCur.moveToNext()) {
                  String phoneNo = pCur.getString(pCur.getColumnIndex(
                  ContactsContract.CommonDataKinds.Phone.NUMBER));
               }
               pCur.close();
            }
         }
      }
      if (cur ! = null) {
         cur.close();
      }
      return nameList;
   }
}
Step 4 − Add the following code to AndroidManifest.xml
<?xml version = "1.0" encoding = "utf-8"?>
<manifest xmlns:android = "http://schemas.android.com/apk/res/android"
   package = "com.example.myapplication">
   <uses-permission android:name = "android.permission.READ_CONTACTS" />
   <application
      android:allowBackup = "true"
      android:theme = "@style/AppTheme.NoActionBar"
      android:icon = "@mipmap/ic_launcher"
      android:label = "@string/app_name"
      android:roundIcon = "@mipmap/ic_launcher_round"
      android:supportsRtl = "true">
      <activity
         android:name = ".MainActivity"
         android:configChanges = "keyboardHidden|orientation|screenSize">
         <intent-filter>
            <action android:name = "android.intent.action.MAIN" />
            <action android:name = "android.intent.action.CREATE_SHORTCUT" />
            <category android:name = "android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –