Duvidas com FormatNumber [RESOLVIDO]

import corejava.*;
public class Numeros{
	public static void main(String[] args){
		double x = 10000.0 / 3.0;
		NumberFormat nf = NumberFormat.getNumberInstance();
		String fx = nf.format(x);
		System.out.println(fx);
	}
}

C:\Samanta\exercicio java8.02\Numeros.java:5: cannot find symbol
symbol  : class NumberFormat
location: class Numeros
		NumberFormat nf = NumberFormat.getNumberInstance();
                ^
C:\Samanta\exercicio java8.02\Numeros.java:5: cannot find symbol
symbol  : variable NumberFormat
location: class Numeros
		NumberFormat nf = NumberFormat.getNumberInstance();
                                  ^
2 errors

Ferramenta concluída com código de saída 1