How to use size() in android CopyOnWriteArraySet?

AndroidMobile DevelopmentApps/Applications

   Before getting into an example, we should know what CopyOnWriteArraySet is. It is a thread-safe variant of ArrayList and operations add, set, and so on by making a fresh copy of the underlying array.

This example demonstrates about How to use size() in android CopyOnWriteArraySet

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 = ""
   xmlns:app = ""
   xmlns:tools = ""
   android:layout_width = "match_parent"
   android:gravity = "center"
   android:layout_height = "match_parent"
   tools:context = ".MainActivity"
   android:orientation = "vertical">
      android:id = "@+id/actionEvent"
      android:textSize = "40sp"
      android:layout_marginTop = "30dp"
      android:layout_width = "wrap_content"
      android:layout_height = "match_parent" />

In the above code, we have taken a text view to show CopyOnWriteArraySet elements.

Step 3 − Add the following code to src/

package com.example.myapplication;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import java.util.concurrent.CopyOnWriteArraySet;
public class MainActivity extends AppCompatActivity {
   CopyOnWriteArraySet copyOnWriteArraySet;
   String head;
   @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
   protected void onCreate(Bundle savedInstanceState) {
      copyOnWriteArraySet = new CopyOnWriteArraySet<String>();
      final TextView actionEvent = findViewById(;
      actionEvent.setText("" + copyOnWriteArraySet);
      actionEvent.setOnClickListener(new View.OnClickListener() {
         public void onClick(View v) {

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 an 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 –

Now click on text view, it will show result as shown below –

Click here to download the project code

Published on 10-Apr-2019 07:42:19