For my class I need to write code that adds up the numbers 1-100 which will produce the number 5050. He told us not to use a main method and use a for loop. Is a main method 'public static void main (String[] args)' or something else. I am just still very confused on what exactly the main method is. Here is the code I have so far that works
public class SumAndAverageForLoop{
public static void main (String[] args) {
int sum = 0;
for (int i = 1; i <= 100; i++) sum += i;
System.out.println("The sum is " + sum);
}
}
From what I read more and after talking to some other kids in the class they said I need to make another class with a main method that calls this class but how do you call one class from another?
How to call one class from another that has a main method?
Yes the public static void main(String[] args)
signature is the main method.
It sounds like you're writing library style code. So just create a method with a meaningful name for what your code does. Like AddOnetoOneHundred
or similar.
You can create a method like this:
public static int CountUp() {
// code that was in your main method before
}
Double check your assignment, your teaching might have specified a class and method name and already has a program that will test your code.
A main method is fundamental to any given program as the Java compiler searches for the method as a starting point of execution. However, you are trying to make a utility class so:
class SumAndAverageForLoop {
// no main method
public static int sum() {
int sum = 0;
for (int i = 1; i <= 100; i++) sum += i;
System.out.println("The sum is " + sum);
}
}
class MainClassProgram {
// main in another class
public static void main() {
SumAndAverageForLoop.sum();
}
}
Try to create a method to do the calculation. The idea is create code that is unit testable.
public class SumAndAverageForLoop{
public static void main (String[] args) {
int returned = SumUp(1, 100);
System.Out.Println("sum is " + returned);
}
public int SumUp(int startInt, int endInt) {
int sum = 0;
if (endInt > startInt) {
for (int i = startInt; i <= endInt; i++) sum += i;
}
return sum;
}
}
Short Answer:
Yes, that ( public static void main (String[] args)
) is the main method.
Long Answer:
The main method is the entry point for an application. Without it, you may have code, but that code must somehow link to a main method or it cannot be ran. Counter-intuitively, the main method doesn't actually have to be a method. In C, you can create an integer array called main and execute it. It will translate the integers into hexadecimal and execute a corresponding Assembly command for each one, iteratively.
If you do what the professor says, you will not be able to test the program as an executable. He probably has a program made to run your code and test it for him, which is why he doesn't want a main method.
I'm not sure by what your teacher means by, "not using a main method". But you can declare a method outside of you main method and call it from there;
public class SumAndAverageForLoop{
public static void main (String[] args) {
makeSum();
}
public static void makeSum() {
int sum = 0;
for (int i = 1; i <= 100; i++) {
sum += i;
}
System.out.println(sum);
}
}
Also, since one of your comments asked "How to create a method?".
I suggest you read up on some books for beginners. I'd recommend the book Head First Java.
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