cant understand calculate method : i have problem in calculate method 

it should do like give me that total price like quantity*5  
it should do like any number*5  like 1*5 =5      2*5 =10

but the problem here if i change the quantity to 2 it will give me the price 20 $

quantity 3 it will give me price 45, while it should price be 15 i tried to search for the problem cant find anything 


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    /**
     * IMPORTANT: Make sure you are using the correct package name.
     * This example uses the package name:
     * package com.example.android.justjava
     * If you get an error when copying this code into Android studio, update it to match teh package name found
     * in the project's AndroidManifest.xml file.
     **/

    package justjava.andriod.example.com.justjava;


    import android.os.Bundle;
    import android.support.v7.app.AppCompatActivity;
    import android.util.Log;
    import android.view.View;
    import android.widget.CheckBox;
    import android.widget.EditText;
    import android.widget.TextView;
    import android.widget.Toast;

    import java.text.NumberFormat;

    import justjava.andriod.example.com.justjava.R;

    /**
     * This app displays an order form to order coffee.
     */
    public class MainActivity extends AppCompatActivity {
        int quantity = 0;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }
        /**
         * This method is called when the plus button is clicked.
         */
        public void increment (View view) {
            // this method to block the user to use increamnt method if the number is 100
            if (quantity==100){
               //show an error message as a toast
                Toast.makeText(this, "you cannot have more than 100 coffes", Toast.LENGTH_SHORT).show();
                // Exit this method early because there's nothing left to do
                return;
            }
            quantity = quantity+1;
            display(quantity);

        }
        /**
         * This method is called when the minus button is clicked.
         */
        public void decrement (View view) {
    // this if statment block user to make decremnt method below number 1 so it wont go to 0
            if (quantity==1) {
                // show an error message as a toast
                Toast.makeText(this, "you cannot have more less than 1 coffee", Toast.LENGTH_SHORT).show();
                // Exit this method early because there's nothing left to do
                return;
            }
            quantity =  quantity - 1;
            display(quantity);
        }



        /**
         * Calculates the price of the order.
         *@return total price

         */
        private String creatOrderSummary(String name, int basePrice, boolean addWhippedCream , boolean addCocolate) {
            String priceMessage = "Name : " + name;
            priceMessage += "\nAdd Whipped Cream? " + addWhippedCream;
            priceMessage += "\nadd chocolate? " + addCocolate;
            priceMessage = priceMessage + "\nQuantity" + quantity;
            priceMessage = priceMessage + "\nTotall: $"+ basePrice;
            priceMessage = priceMessage + "\nthank you!";
            return priceMessage;


        }


        /**
         * Calculates the price of the order.
         *@return total price

         */
        private int calculatePrice(boolean addWhippedCream, boolean addChocolate ) {
            // pice of 1 cup of coffe
            int basePrice = quantity *5;
            // add $1 if the user wants whipped cream
            if (addChocolate) {
                basePrice = basePrice + 1;
            }
            // add $2 if the user wants chocolate
            if (addChocolate) {
                basePrice = basePrice + 2;
            }

            // calcuate the tottal order price by multiplying by quantity
            return quantity * basePrice;

        }



        /**
         * This method is called when the order button is clicked.
         */
        public void submitOrder(View view) {
            // find the user's name
            EditText text = (EditText) findViewById(R.id.name_field);
            String name = text.getText().toString();
            // figure it out if user wants whipped cream topping
            CheckBox whippedCreamCheckBox = (CheckBox) findViewById(R.id.whipped_cream_checkbox);
            boolean hasWippedCream = whippedCreamCheckBox.isChecked();
            Log.v("MainActivity", "Has whipped cream: " + hasWippedCream);
            // figure it out if user want chocolate
            CheckBox chocolate = (CheckBox) findViewById(R.id.add_chocolate);
            boolean hasCocolate = chocolate.isChecked();

            int price = calculatePrice(hasWippedCream, hasCocolate);
            String priceMessage = creatOrderSummary(name,price, hasWippedCream, hasCocolate);
            displayMessage(priceMessage);

        }

        /**
         * This method displays the given quantity value on the screen.
         */
        private void display(int number) {
            TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);
            quantityTextView.setText("" + number);

        }





        /**
         * This method displays the given text on the screen.
         */
        private void displayMessage(String message) {
            TextView orderSummaryTextView = (TextView) findViewById(R.id.order_summary_text_view);
            orderSummaryTextView.setText(message);
        }


    }


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