import javax.swing.*;

public class Tokenize{
	public static String s[] = new String[100];
	public static void main (String args[]){
		String ask = JOptionPane.showInputDialog("Enter:");
	public static void isAsk(String ask){
		StringTokenizer st = new StringTokenizer(ask," ",false);
		int input = Integer.parseInt(st.nextToken());

Here is the sample:
Enter: 1 2 3

I want to output 2, but it only output 1. What will i have to do with my code so that i can output either 1 or 2 or 3. Thank you ahead for the help.

You need to loop your code to print all the tokens. Something like:

    // parse every token OR print it OR do whatever

Since currently there is no loop, it exits after printing just the first token.

Also note, the StringTokenizer class is a legacy class and maintained just for compatability reasons, it's use si discouraged. Use String.split() instead.