/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
/* 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 sem dígitos
		String s = "abcdef";
		Pattern p = Pattern.compile("[0-9]{6}");
		Matcher m = p.matcher(s);
		m.find();
		// find não encontrou nada, group lança exceção
        System.out.println(m.group());
    }
}

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