[yellowbus]

I have a "non-static method cannot be referenced from a static context" problem. I've research similar cases in google, but I can't make the error go away no matter what.
Sry for being nubby. barely one year of programming:(
Basically, I'm trying to call a method from another class, and make it print on screen.

public class Show{
   public static void main(String[] args) {
		int x=1;
		int a=4;
		int b=2;
		x = Combination.comb(a,b);
		System.out.println(x);
	}	}

This is the Combination class that i am trying to call. first method does factorials, second method uses factorials to do combination

public class Combination {

	
public int factorial(int x) {
int result=1;
for(int i=1;i<=x;i++){
	result=i * result;
}
return result;
}

public int comb(int n, int k)
{
int combin=1;
int temp4=1;
int temp1 = factorial(n);
int temp2 = factorial(k);
temp4 = n-k;
int temp3 = factorial (temp4);
combin = temp1/(temp2 * temp3);
return combin;
}
}

[Martyr2]

You simply have to make the functions of your class static. Since you are not creating instances of your classes, and thus wanting to use methods statically, you simply have to declare the methods static as so...

public static int factorial(int x) {

and 

public static int comb(int n, int k) {

Just drop in the word static between the modifier and the return type and recompile. You are all ready to go.

This post has been edited by Martyr2: 07 September 2007 - 06:36 PM

[yellowbus]

thank you, i've read similar solutions to this problem but i couldn't apply it to my own program (newb-ness). it works perfectly, thanks for the fast reply

[ajwsurfer]

The reason you need to make these static is that no classes are defined as instances (like Martyr2 said). I just want to clarify what he said:

  Combination comb1 = new Comination();
  // or
  Combination comb2;

[yellowbus]

I had another program with the same program problem, and i tried to switch double perimeters = perimeter(s1,s2,s3);
with
perimeters = new perimeter();
just like ajwsurfer said, but then i got even more errors (nonstatic method perimeter(double,double,double) cannot be referenced from static context). i put astericks on the problem lines. can anyone help me? i tried to apply the same solution but it wouldn't work.

public class triangle{
   public static void main(String[] args) {

double s1=0;
double s2=0;
double s3=0;

	System.out.println("Enter side 1 of the triangle:");
	s1 = TextIO.getlnInt();
	System.out.println("Enter side 2 of the triangle:");
	s2 = TextIO.getlnInt();
		System.out.println("Enter side 3 of the triangle:");
	s3 = TextIO.getlnInt();
	

	***double perimeters = perimeter(s1,s2,s3);
	***double areas  = area(s1,s2,s3);
	System.out.println("Perimeter is " + perimeters);
	System.out.println("Area is " + areas);
   }

   
   	public double perimeter(double s1, double s2, double s3){	
   		double peri;
   		peri = s1 + s2 + s3;
   		return peri;
   	}
   	
   	public double area(double s1, double s2, double s3){	
   		double area1;
   		double temp;
   		temp = (s1 + s2 + s3)/2;
   		area1 = temp * (temp-s1) * (temp-s2) * (temp-s3);
   		return area1;
   	}
   	
   	
   	
   
   }

[Martyr2]

Again you need to put static on both of your functions since you are calling them from static main(). Whenever you call another local function from main (which is static) then they have to be static too. That is just the general rule.