Thread: Java application for infinite series that calculates pi

Hi

I am having trouble compiling my code for a java application that is supposed to print out the infinite series for Pi. Here is my java code:

//a java application that generates the infinite series for Pi, ie 3.14159...=4-4/3+4/5-4/7+4/9
 
public class Pi{
 
	public static void main(String args[]){
 
//declare and initialize variables
 
long counter=1;
double pi;
 
 
double total=0;
 
for(counter=1; counter<=1000; counter++)
 
pi=4+4*(Math.pow(-1,counter))/(2*counter+1);
 
 
 
total=total+pi;
 
System.out.printf("Infinite series for Pi is %f", total);
 
}//end main
 
}//end class

Here is the error in my output that results when I attempt to compile my code:

C:\Users\anonymous\Desktop\chapter five exercises for java\Pi.java:21: error: variable pi might not have been initialized
total=total+pi;
^
1 error

Tool completed with exit code 1

Why do I need to initialized pi when I already initialized the total?

Nevermind , problem solved

You should always initialise variables with a value. If they're not given a value, they get assigned null.

Originally Posted by CDeighan

You should always initialise variables with a value. If they're not given a value, they get assigned null.

This is not true for primitives, and only true for class variables. See Norm's answer.

And, actually, you should /not/ always explicitly assigned class variables, primitives or objects. Many compilers actually do (or did -- you'd have to look at the bytecode) not optimize the unneeded assigment to 0 or null away. That is, they emit larger code for the class.

Of course, in this case, the class variable does need to be assigned to some default prior to be used on the right-hand side of an assignment, because the compiler can't be sure it was assigned something in the loop.

In many cases lke this I will show the assignment to a default directly above the condition that will probably change it, so the state of the property is determined in the same chunk of code.

In general, the only reason to have declared but uninitialized class variables is if they are also class properties. In which case there will, or should, be setters, getters and or initializers in constructors.

Otherwise, declare and, if necessary, initialize them as needed. This isn't C, so don't bother with declaring plain old variables up front. Of course, when doing toy apps like this, with everything in main(), the line between class variables, locals and properties is blurred. Java, unlike C#, doesn't actually enforce this distinction, so it is up to the person between the keyboard and the chair to understand what they are doing.