/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String msgbody = "For User: 987 ID:4321";
		Pattern idPatt = Pattern.compile("^(?:For User: \\S+ ID:|ID is )(\\d+)$");
		Matcher m = idPatt.matcher(msgbody);
		if (m.find()) {
			System.out.println("Matched: " + m.group(1));
		} else {
			System.out.println("Invalid message body");
		}
	}
}

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