title: For loop printing twice sometimes
body: <p>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:</p>
  
  <pre><code>Converting values to Euros.
  £4.00 &gt;&gt;&gt; €5.45
  £123.44 &gt;&gt;&gt; €168.13
  Converting values to Euros.
  £4.00 &gt;&gt;&gt; €5.45
  £123.44 &gt;&gt;&gt; €168.13
  </code></pre>
  
  <p>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:</p>
  
  <pre><code>    import java.util.Scanner;
  import java.text.DecimalFormat;
  import java.util.ArrayList;
  public class Conversion {
  
      public void mainMenu(Scanner scan, ArrayList&lt;Double&gt; 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&lt;Double&gt; 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&lt;Double&gt; values, DecimalFormat twoDecimal) {
  
          System.out.println("Converting values to Euros.");
  
          for (int i = 0; i &lt; values.size(); i++) {
              System.out.println("£" + twoDecimal.format(values.get(i)) + " &gt;&gt;&gt; " + "\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&lt;Double&gt; values = new ArrayList&lt;Double&gt;();
          DecimalFormat twoDecimal = new DecimalFormat("0.00");
  
          conv.mainMenu(scan, values, twoDecimal);
  
          scan.close();
  
      }
  
  }
  </code></pre>