Problem
I am a beginner and I wanted to make programs that would help me while I learnt Java. I made a program to help me in my assignments. Any suggetions?
Main method
public class MirrorFormula {
public static void main(String[] args) {
Scanner keyboardInput = new Scanner(System.in);
double u =0;
double v =0;
double f =0;
System.out.println("Hello! This is a calculator based on the Mirror Formula. n");
System.out.println("The mirror formula is a relation between the object distance, the image distance n and the focal length.");
System.out.println("The formula is : 1/u + 1/v = 1/f. (u=distance of object, v=distance of image, f=focal length.)");
System.out.println("It is applicable for both convex mirrors and concave mirrors.");
System.out.println();
System.out.println("This calculator can calculate :");
System.out.println();
System.out.println("1. Distance of the object from the pole of the spherical mirror.");
System.out.println("2. Distance of the image from the pole of the spherical mirror.");
System.out.println("3. Focal length");
System.out.println("[If you have 2 of the values.]");
System.out.println("________________________________________________________________________________________________________________________________");
System.out.println("What value would you like to find out? ");
System.out.println("Enter: n 1. for Distance of object n 2. for distance of image n 3. for Focal length n (Please note that you don't need to enter units. The ans. is in whatever unit you enter the values)" );
int userChoice = keyboardInput.nextInt();
System.out.println("________________________________________________________________________________________________________________________________");
switch (userChoice) {
case 1 :
System.out.println("Please enter the distance of the image: ");
v = keyboardInput.nextDouble();
System.out.println("Please enter the focal length: ");
f = keyboardInput.nextDouble();
u = findU(v, f);
break;
case 2 :
System.out.println("Please enter the distance of the object: ");
u = keyboardInput.nextDouble();
System.out.println("Please enter the focal length: ");
f = keyboardInput.nextDouble();
v = findV(u, f);
break;
case 3 :
System.out.println("Please enter the distance of the object: ");
u = keyboardInput.nextDouble();
System.out.println("Please enter the distance of the image: ");
v = keyboardInput.nextDouble();
f = findF(u, v);
break;
}
System.out.println("___________________________________________________");
System.out.println(" Distance of the object from the pole is | " + u + " |");
System.out.println(" Distance of the image from the pole is | " + v + " |");
System.out.println(" The focal length | " + f + " |");
System.out.println("___________________________________________________");
}
Other methods
These calculate the ans. based on the input:
public static double findU(double v, double f) {
double oneUpon;
oneUpon = 1/f - 1/v;
return 1/oneUpon;
}
public static double findV(double u, double f){
double oneUpon;
oneUpon = 1/f - 1/u;
return 1/oneUpon;
}
public static double findF(double u, double v){
double oneUpon = 1/u + 1/v;
return 1/oneUpon;
}
}
Solution
First, the findX functions don’t need to initialise the variable oneUpon inside. It’s also unclear, anyway.
public static double findU(double v, double f) {
double oneUpon;
oneUpon = 1/f - 1/v;
return 1/oneUpon;
}
public static double findV(double u, double f){
double oneUpon;
oneUpon = 1/f - 1/u;
return 1/oneUpon;
}
public static double findF(double u, double v){
double oneUpon = 1/u + 1/v;
return 1/oneUpon;
}
Just return the variable directly.
I’d also like to point out that findU and findV are identical in function, just named differently.
Consider the following instead:
public static double findUV(double uv, double f) {
return 1/(1/f - 1/uv);
}
public static double findF(double u, double v){
return 1/(1/u + 1/v);
}
System.out.println("Hello! This is a calculator based on the Mirror Formula. n");
System.out.println("The mirror formula is a relation between the object distance, the image distance n and the focal length.");
System.out.println("The formula is : 1/u + 1/v = 1/f. (u=distance of object, v=distance of image, f=focal length.)");
System.out.println("It is applicable for both convex mirrors and concave mirrors.");
System.out.println();
System.out.println("This calculator can calculate :");
System.out.println();
System.out.println("1. Distance of the object from the pole of the spherical mirror.");
System.out.println("2. Distance of the image from the pole of the spherical mirror.");
System.out.println("3. Focal length");
System.out.println("[If you have 2 of the values.]");
This is not how you print large blocks. Separate your strings with line separators like /n. Keep the text as a large multi-line string block, and print that out instead. It will take less maintenance and less System.out.println calls.
Feel free to take the user input as a string/letter instead of an integer, makes everything much clearer. On a related note, an exit function would be nice too.
switch (userChoice) {
case 1 :
FunU and FindV do the same thing you should find an appropriate name for the operation it does instead. Consider changing your function findV to
return (f * u) / (u - f);
You can change findF in a similar way. More importantly functions findV and findU will fail when both parameters are equal. (Division by zero).