Java array.add() stops the program

Question

I managed to dynamically add an element in my array, but unfortunately the program stops. How can I continue it? Thank you!

....

List<String> messages = Arrays.asList("Mary", "Nadia!", "Drake");

System.out.println("Enter Costumer's Name:"); 
cust_name =in.next();
if(cust_name .equals("Mary"))
System.out.println("Already a member!");
else if (cust_name .equals("Nadia"))
System.out.println("Already a member!");
else if(cust_name .equals("Drake"))
System.out.println("Already a member!");
else
messages.add(in.next());
System.out.println("Not a member! " + cust_name + " just added.");

....

When you program stops, it should tell you what went wrong. There will be an exception with description and a stack trace. Please post the errors. — clcto
– clcto, Commented Apr 1, 2014 at 19:49
stacktrace required, also instead of checking hardcoded for each element you should check if(messages.contains(cust_name)) — Jigar Joshi
– Jigar Joshi, Commented Apr 1, 2014 at 19:50
An alternative to what you're doing here is to use a Set<String> (such as HashSet) to store the name. When you add something to a Set, the value returned is a boolean, which tells you whether the value is actually new - and you could print the appropriate message depending on that value. It will make your code shorter and cleaner. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Apr 1, 2014 at 20:05

Elliott Frisch · Accepted Answer · 2014-04-01 19:49:24Z

2

Arrays.asList() returns a fixed size List, the easiest fix I can think of is -

List<String> messages = new ArrayList<String>(
    Arrays.asList("Mary", "Nadia!", "Drake")
); // Creates a new (mutable) list.

answered Apr 1, 2014 at 19:49

Elliott Frisch

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Steve Kuo · Accepted Answer · 2014-04-01 19:59:49Z

2

The List that Arrays.asList returns is fixed size. Trying to add to it will result in an exception.

If you want a dynamic list initialized to some values then do something like:

List<String> messages = new ArrayList<String>(Arrays.asList("Mary", "Nadia!", "Drake"));

Or better yet use Google Guava's Lists.newArrayList

List<String> messages = Lists.newArrayList("Mary", "Nadia!", "Drake");

edited Apr 1, 2014 at 19:59

answered Apr 1, 2014 at 19:48

Steve Kuo

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2 Comments

Jigar Joshi Over a year ago

I don't think so docs.oracle.com/javase/7/docs/api/java/util/…

Jigar Joshi Over a year ago

Oops answer edited :) , initially it said it returns immutable instance and can't be modified

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