Help with Double.NaN

Question

This class is supposed to check how many real numbers are being sent to All and depending on that perform further operations with those numbers.
It works just fine if all four number are present, but if one number is missing (i.e. fourth number in n2 in main), when it goes to All the first condition is ALWAYS true, even though it says if the number is not NaN it just skips it and goes to AllN with four numbers. Am I not using Double.NaN right?
public class Numbers {
public double num1 = Double.NaN, num2 = Double.NaN;
public double num3 = Double.NaN, num4 = Double.NaN;
public double first = Double.NaN, second = Double.NaN;
public double third = Double.NaN, fourth = Double.NaN;
public String snum0;
// accessor methhods
public void setNum1 (double value) {
num1 = value;
public void setNum2 (double value) {
num2 = value;
public void setNum3 (double value) {
num3 = value;
public void setNum4 (double value) {
num4 = value;
public double getNum1 () {
return num1;
public double getNum2 () {
return num2;
public double getNum3 () {
return num3;
public double getNum4 () {
return num4;
public double getFirst () {
if (first != Double.NaN)
return first;
else
return Double.NaN;
public double getSecond () {
if (second != Double.NaN)
return second;
else
return Double.NaN;
public double getThird () {
if (third != Double.NaN)
return third;
else
return Double.NaN;
public double getFourth () {
if (fourth != Double.NaN)
return fourth;
else
return Double.NaN;
public void All (Numbers s) {
if (s.num4 != Double.NaN &&
s.num3 != Double.NaN &&
s.num2 != Double.NaN &&
s.num1 != Double.NaN)
AllN(s.num1, s.num2, s.num3, s.num4);
else if (s.num4 == Double.NaN &&
s.num3 != Double.NaN &&
s.num2 != Double.NaN &&
s.num1 != Double.NaN)
AllN(s.num1, s.num2, s.num3);
else if (num4 == Double.NaN &&
num3 == Double.NaN &&
num2 != Double.NaN &&
num1 != Double.NaN)
AllN(num1, num2);
else if (s.getNum4() == Double.NaN &&
s.getNum3() == Double.NaN &&
s.getNum2() == Double.NaN &&
s.getNum1() != Double.NaN)
AllN(num1);
else if (s.getNum4() == Double.NaN &&
s.getNum3() == Double.NaN &&
s.getNum2() == Double.NaN &&
s.getNum1() == Double.NaN)
AllN();
}// end SortAll
public void AllN() {
snum0 = "There are no numbers to sort";
public static void main (String args[]) {
Sort n1 = new Sort();
n1.setNum1(13);
n1.setNum2(14);
n1.setNum3(15);
n1.setNum4(16);
n1.SortAll(n1);
Sort n2 = new Sort();
n2.setNum1(57);
n2.setNum2(34);
n2.setNum3(50);
n2.SortAll(n2);
System.out.println(n1.getSecond());
System.out.println(n2.getFirst());
} // End Main

Answer 1

double v = 5.0;
if (v == v) {
  System.out.println("v is a number: "+v);
} else { // (v != v)
  System.out.println("v is not a number: "+v);
// or
if (Double.isNaN(v)) {
  System.out.println("v is not a number: "+v);
} else {
  System.out.println("v is a number: "+v);
}