How to add multiple data to Firestore | Batched Writes (Android)

MainActivity.java

package com.oliverstudio.firestoreadmintest1;
 
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
 
import androidx.appcompat.app.AppCompatActivity;
 
import com.google.firebase.firestore.CollectionReference;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.WriteBatch;
 
import java.util.Random;
 
public class MainActivity extends AppCompatActivity {
 
    private Button mWriteButton;
    private ProgressBar mProgressBar;
 
    private FirebaseFirestore mDB;
    private CollectionReference mCollectionRef;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        initViews();
 
        mDB = FirebaseFirestore.getInstance();
        mCollectionRef = mDB.collection("users");
 
        mWriteButton.setOnClickListener(view -> {
 
            showProgressBar(true);
 
            WriteBatch batch = mDB.batch();
            for (int i = 0; i < 100; i++) {
                batch.set(mCollectionRef.document(), new Character("Name" + i, new Random().nextInt(100)));
            }
            batch.commit().addOnSuccessListener(aVoid -> {
                showProgressBar(false);
            }).addOnFailureListener(e -> {
                showProgressBar(false);
            });
 
        });
 
    }
 
    private void showProgressBar(boolean show) {
        if (show) {
            mWriteButton.setVisibility(View.GONE);
            mProgressBar.setVisibility(View.VISIBLE);
        } else {
            mProgressBar.setVisibility(View.GONE);
            mWriteButton.setVisibility(View.VISIBLE);
        }
    }
 
    private void initViews() {
        mWriteButton = findViewById(R.id.write_btn);
        mProgressBar = findViewById(R.id.progress_bar);
    }
}