How to check existence of an element in android listview?

This example demonstrate about How to check existence of an element in android listview.
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical"
   android:gravity="center_horizontal"
   android:layout_marginTop="30dp"
   tools:context=".MainActivity">
   <EditText
      android:id="@+id/edit_query"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" />
   <Button
      android:id="@+id/buttonPanel"
      android:text="Check"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content" />
   <ListView
      android:id="@+id/list"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content">
   </ListView>
</LinearLayout>
In the above code, we have taken editext, button and listview. When user click on button after inserting value in edittext,it will do data validation with listview items.
Step 3 − Add the following code to src/MainActivity.java
package com.example.myapplication;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.Arrays;

public class MainActivity extends AppCompatActivity {
   ListView list;
   String[] mobileArray = {"Android", "IPhone", "WindowsMobile", "Blackberry", "WebOS", "Ubuntu", "Windows7", "Max OS X"};
   EditText edit_query;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      edit_query = findViewById(R.id.edit_query);
      list = findViewById(R.id.list);
      final ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(mobileArray));
      findViewById(R.id.buttonPanel).setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            if(!edit_query.getText().toString().isEmpty()) {
               if(arrayList.contains(edit_query.getText().toString())) {
                  Toast.makeText(MainActivity.this,"Already it is in list",Toast.LENGTH_LONG).show();
               } else {
               arrayList.add(edit_query.getText().toString());
               ArrayAdapter adapter = new ArrayAdapter<String>(MainActivity.this,
               android.R.layout.simple_list_item_1, arrayList);
               list.setAdapter(adapter);
            }
          }
      }
    });

      ArrayAdapter adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList);
      list.setAdapter(adapter);
   }
}
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 –
In the above result, we have added element to listview, now enter same value to do data validation as shown below –
Click here to download the project code