For loop printing twice sometimes

Question

In my convertEuro method the for loop is causing the output to be printed twice, but only sometimes. What I mean is this is what gets displayed:

Converting values to Euros.
£4.00 >>> €5.45
£123.44 >>> €168.13
Converting values to Euros.
£4.00 >>> €5.45
£123.44 >>> €168.13

During testing it seems to do this maybe 2 times out of 10, and I can't figure out why. Code below if someone can please help:

    import java.util.Scanner;
import java.text.DecimalFormat;
import java.util.ArrayList;
public class Conversion {

    public void mainMenu(Scanner scan, ArrayList<Double> values, DecimalFormat twoDecimal) {

        int menuChoice;

        System.out.println("1. Enter values and type -1 to stop");
        System.out.println("2. Euros");
        System.out.println("3. Dollars");
        System.out.println("4. Yen");
        System.out.println("5. Rupees");
        System.out.println("6. Exit");

        menuChoice = scan.nextInt();

        switch (menuChoice) {
        case 1:

            enterValues(scan, values, twoDecimal);

        case 2:

            scan.nextLine();
            convertEuro(scan, values, twoDecimal);

        }

    }

    public void enterValues(Scanner scan, ArrayList<Double> values, DecimalFormat twoDecimal) {
        double value = 0;

        do {
            System.out.print("Enter value. Enter -1 to stop: £");



            while (!scan.hasNextDouble()) {
                System.out.print("Please enter a double (£xx.xx): £");
                scan.nextLine(); //Consumes \n
                scan.next();
            }

            value = scan.nextDouble();

            if (value != -1) {
                values.add(value);
                System.out.println("Value entered.");
            }

        }
        while (value != -1);


        System.out.println("Returning to main menu. ");
        mainMenu(scan, values, twoDecimal);

    }

    public void convertEuro(Scanner scan, ArrayList<Double> values, DecimalFormat twoDecimal) {

        System.out.println("Converting values to Euros.");

        for (int i = 0; i < values.size(); i++) {
            System.out.println("£" + twoDecimal.format(values.get(i)) + " >>> " + "\u20ac" + twoDecimal.format(values.get(i) * 1.362));
        }
    }

    public static void main(String[] args) {

        Conversion conv = new Conversion();
        Scanner scan = new Scanner(System.in);
        ArrayList<Double> values = new ArrayList<Double>();
        DecimalFormat twoDecimal = new DecimalFormat("0.00");

        conv.mainMenu(scan, values, twoDecimal);

        scan.close();

    }

}

Answer 1

You need to add a break; statement:

case 1:
    enterValues(scan, values, twoDecimal);
    break;

Answer 2

When the switch statement hits the correct case, it executes it and proceeds executing other cases which are below until and unless it hit an break statement.

The correct process is

 switch (menuChoice) {
        case 1:
            enterValues(scan, values, twoDecimal);
            break;
        case 2:
            scan.nextLine();
            convertEuro(scan, values, twoDecimal);
            break;
        }

Thats why best practice is to put break statement after every case end.

Thank you