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How to get the duplicates values from Arraylist and then get those items in another Arraylist in Android?
This example demonstrate about How to get the duplicates values from Arraylist<String> and then get those items in another Arraylist.
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"?> <android.support.constraint.ConstraintLayout xmlns:android = "http://schemas.android.com/apk/res/android" xmlns:app = "http://schemas.android.com/apk/res-auto" xmlns:tools = "http://schemas.android.com/tools" android:layout_width = "match_parent" android:layout_height = "match_parent" tools:context = ".MainActivity"> <ListView android:id = "@+id/list" android:layout_width = "wrap_content" android:layout_height = "wrap_content" /> </android.support.constraint.ConstraintLayout>
In the above code, we have taken listview to show duplication list items from array list.
Step 3 − Add the following code to src/MainActivity.java
package com.example.andy.myapplication;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;
public class MainActivity extends AppCompatActivity {
ListView list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Set<String> set = new HashSet<>();
ArrayList<String> MainListItem = new ArrayList<String>();
MainListItem.add("Sai");
MainListItem.add("Sai");
MainListItem.add("ram");
MainListItem.add("Sai krishna");
MainListItem.add("Sai Ram Krishna");
MainListItem.add("tutorialspoint.com");
MainListItem.add("tutorialspoint.com");
ArrayList<String> duplicates = new ArrayList<String>();
for (String s : MainListItem) {
if (!set.add(s)) {
duplicates.add(s);
}
}
list = findViewById(R.id.list);
ArrayAdapter arrayAdapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1, duplicates);
list.setAdapter(arrayAdapter);
}
}In the above code we have taken arraylist as shown below –
ArrayList<String> MainListItem = new ArrayList<String>();
MainListItem.add("Sai");
MainListItem.add("Sai");
MainListItem.add("ram");
MainListItem.add("Sai krishna");
MainListItem.add("Sai Ram Krishna");
MainListItem.add("tutorialspoint.com");
MainListItem.add("tutorialspoint.com");In the above code “sai” and “tutrialspoint.com” are duplicated values.
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, it has shown duplicated values from arraylist.
Click here to download the project code
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