How to use subList() in android CopyOnWriteArrayList?

Before getting into the example, we should know what CopyOnWriteArrayList 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 subList() in android CopyOnWriteArrayList

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 = "https://schemas.android.com/apk/res/android"
   xmlns:app = "https://schemas.android.com/apk/res-auto"
   xmlns:tools = "https://schemas.android.com/tools"
   android:layout_width = "match_parent"
   android:gravity = "center"
   android:layout_height = "match_parent"
   tools:context = ".MainActivity"
   android:orientation = "vertical">
   <TextView
      android:id = "@+id/actionEvent"
      android:textSize = "40sp"
      android:layout_marginTop = "30dp"
      android:layout_width = "wrap_content"
      android:layout_height = "match_parent" />
</LinearLayout>

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

Step 3 − Add the following code to src/MainActivity.java

package com.example.myapplication;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CopyOnWriteArrayList;
public class MainActivity extends AppCompatActivity {
   CopyOnWriteArrayList copyOnWriteArrayList;
   String head;
   @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      copyOnWriteArrayList = new CopyOnWriteArrayList<String>();
      final TextView actionEvent = findViewById(R.id.actionEvent);
      copyOnWriteArrayList.add("sai");
      copyOnWriteArrayList.add("ram");
      copyOnWriteArrayList.add("krishna");
      copyOnWriteArrayList.add("prasad");
      copyOnWriteArrayList.add("ram");
      actionEvent.setText("" + copyOnWriteArrayList);
      actionEvent.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            actionEvent.setText("" + copyOnWriteArrayList.subList(0,2));
         }
      });
   }
}

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 –

Click on textview, It will give the result as shown below –