Java - Como quitar decimales??

double x = 0.20752992072049992;

String cad=String.valueOf(x);

cad = cad.substring(0,5);    // y tendras "0.207"

x = Double.parseDouble(cad);   // y tendras 0.207

double num=1234.567;

num=Math.rint(num*10)/10;

double num=1234.567;

num=Math.rint(num*100)/100;

double num=1234.567345;

num=Math.rint(num*1000)/1000;

private static String quitarDecimales(String num, int n_decimales) {

    int indice = num.indexOf(".");

    return indice + n_decimales < num.length() ? num.substring(0, indice + n_decimales+1)

        :num.substring(0, num.length());

}

public static void main(String arg[]){

    double num=0.20752992072049992;

    String formatoNum=quitarDecimales(num+"", 3);

    System.out.println(""+formatoNum);

}