This code doesn't work. Why? thanks.

[seanzhang]

import java.util.ArrayList;

import java.util.Scanner;

public class SimpleEventDemo {
/** Main method */
public static void main(String[] args) {

ArrayList<Integer> numbers = new ArrayList<Integer>();

// Create a Scanner
Scanner input = new Scanner(System.in);

// Read all numbers
while(input.hasNextInt()){
System.out.print("Enter a number: ");

// Convert string into integer
numbers.add(input.nextInt());
}
System.out.print(numbers);
}
}

[Norm]

What's it supposed to do?
Please explain what the problem is or why the output of the program is wrong

[seanzhang]

It creates an arraylist and then it prompts user for numbers to populate the list.
And then it prints out the list.

[Norm]

Ok, you've answered the first question. Now how about this one:

Please explain what the problem is or why the output of the program is wrong

[seanzhang]

The while loop doesn't work. If I remove the while loop. It takes one number and it adds the number to the list and prints it out. But with the while loop the program just hangs.

[Norm]

Ok, now we know the problem

Can you copy the console from when you run the code and paste it here?

[seanzhang]

it doesn't run, it just freezes

[Norm]

Its running and waiting for you.
Enter a number.

[seanzhang]

you are right. for some reason it doesn't print "Enter a number: " first time.
Thanks.

[Norm]

That should tell you something about what the hasNextInt() method is doing.

Read the API doc for an explanation:

Both hasNext and next methods may block waiting for further input.

[Singing Boyo]

Converting the while loop to a do-while loop could work. Check it for bugs if the first input isn't actually an integer though... (i.e. I haven't tested this at all)