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Java

Posted by Henrik Christensen
.a{fill-rule:evenodd;}techdegree
Henrik Christensen
Python Web Development Techdegree Student 38,322 Points

Why is it being printed in the wrong order?

I'm having a problem with my output being printed in the wrong order :-/

When I run the code I get this output in the console:

new timer - Set and run a new timer
start - Start timer (45 minutes)
quit - Exit the program

but I was actually expecting:

start - Start timer (45 minutes)
new timer - Set and run a new timer
quit - Exit the program

my code

    private BufferedReader reader;
    private Map<String, String> menu;
    private Timer timer;

    public TimeForBreak() {
        reader = new BufferedReader(new InputStreamReader(System.in));
        menu = new HashMap<String, String>();
        menu.put("start", "Start timer (45 minutes)");
        menu.put("new timer", "Set and run a new timer");
        menu.put("quit", "Exit the program");
    }

    private String promptAction() throws IOException {
        for (Map.Entry<String, String> option : menu.entrySet()) {
            System.out.printf("%s - %s%n",
                    option.getKey(),
                    option.getValue());
        }
        System.out.print("What do you want to do? ");
        String choice = reader.readLine();
        return choice.trim().toLowerCase();
    }

1 Answer

andren
andren
28,558 Points

That happens because HashMap is not ordered, the documentation for the class explicitly states:

This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.

Which means that you should not use HashMap if the order of the keys is of any importance to you.

If you want a map that is ordered based on insertion then you should use the LinkedHashMap class instead.

Henrik Christensen
.a{fill-rule:evenodd;}techdegree
Henrik Christensen
Python Web Development Techdegree Student 38,322 Points

Voila, that fixed it!

Thank you very much :-D