void handlePurchases(List<Purchase>  purchases) {
       String str;
       int numberOfPurchases = 0;

       for(Purchase purchase:purchases) {
           switch(purchase.getPurchaseState()) {
               case Purchase.PurchaseState.PURCHASED:
                   if (!verifyValidSignature(purchase.getOriginalJson(), purchase.getSignature())) {
                       // Invalid purchase
                       // show error to user
                       Toast.makeText(getApplicationContext(), "Error : Invalid Purchase", Toast.LENGTH_SHORT).show();
                       return;
                   }
                   // else purchase is valid
                   //if item is purchased and not acknowledged
                   if (!purchase.isAcknowledged()) {
                       AcknowledgePurchaseParams acknowledgePurchaseParams =
                               AcknowledgePurchaseParams.newBuilder()
                                       .setPurchaseToken(purchase.getPurchaseToken())
                                       .build();
                       mBillingClient.acknowledgePurchase(acknowledgePurchaseParams, ackPurchase);
                   }
                   //else item is purchased and also acknowledged
                   else {
                       numberOfPurchases++;

                       // HOW DOES IT KNOW IF IT IS CONSUMED???

                       // DONT DELETE - if you want to keep on consuming
                       // ConsumeParams consumeParams = ConsumeParams.newBuilder()
                       //        .setPurchaseToken(purchase.getPurchaseToken())
                       //        .build();
                       //
                       //ConsumeResponseListener consumeResponseListener = new ConsumeResponseListener() {
                       //    @Override
                       //    public void onConsumeResponse(BillingResult billingResult, String purchaseToken) {
                       //
                       //        Toast.makeText(DiamondsActivity.this, "Purchase successful", Toast.LENGTH_SHORT).show();
                       //
                       //        if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
                       //
                       //            if (purchase.getSku().equalsIgnoreCase(ITEM_SKU_diamond_500)) {
                       //                Toast.makeText(DiamondsActivity.this, "Thank you for purchasing!", Toast.LENGTH_SHORT).show();
                       //            }
                       //        }
                       //    }
                       //};
                       //billingClient.consumeAsync(consumeParams, consumeResponseListener);
                   }
                   break;
               case Purchase.PurchaseState.PENDING:
                   Toast.makeText(getApplicationContext(), "Purchase is Pending. Please complete Transaction", Toast.LENGTH_SHORT).show();
                   break;
               case Purchase.PurchaseState.UNSPECIFIED_STATE:
                   Toast.makeText(getApplicationContext(), "Purchase Status Unknown", Toast.LENGTH_SHORT).show();
                   break;
           }
       }
   }

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:text="Menu"
        android:textSize="50sp" />

    <EditText
        android:id="@+id/editTextTextMultiLine"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:gravity="start|top"
        android:inputType="textMultiLine"
        android:text="Select a layout type to view an example. The onClick atribute of each button will call a method which executes setContentView to load the new layout." />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>