What did i do wrong

Question

I inserted a new method into the code, and it seems to work alright, but it doesn't solve the problem.
import java.util.*;
public class Summer
   public static void main (String[] args)
     Scanner in = new Scanner(System.in);
     int first = 0;
     int last = 0;
     int total = 0;
     int i = 0;
     System.out.println("Hello. I will calculate the sum");
     System.out.println("of consecutive integers.");
     System.out.println("Please enter the starting number:");
     first = in.nextInt();
     System.out.println("Please enter the ending number:");
     last = in.nextInt();
     while (last < first)
       System.out.println(last + " is smaller than " + first);
       System.out.println("The ending number must be bigger than the first");
       System.out.println("Enter the starting number again");
       first = in.nextInt();
       System.out.println("Enter the ending number again");
       last = in.nextInt();
       System.out.println("The sum of the numbers are " + total);
       total = sum(last, first);
             for (i = first; i <= last; i++)
         total = total + i;     
              public static int sum(int num1, int num2)
                   int result;
                   result = num1 + num2;
                   return result;
}what did i do wrong?

Answer 1

I'm going to try to list the things you could fix here to make this better code. It might seem like a lot and I'm not trying to be mean or rude, I'm just trying to be helpful.
First this part of your code:
System.out.println("Hello. I will calculate the sum");
     System.out.println("of consecutive integers.");
     System.out.println("Please enter the starting number:");
     first = in.nextInt();
     System.out.println("Please enter the ending number:");
     last = in.nextInt();
     while (last < first)
       System.out.println(last + " is smaller than " + first);
       System.out.println("The ending number must be bigger than the first");
       System.out.println("Enter the starting number again");
       first = in.nextInt();
       System.out.println("Enter the ending number again");
       last = in.nextInt();
       System.out.println("The sum of the numbers are " + total);
       total = sum(last, first);
     }This code is repetitive and can be shortened greatly. Notice that the result you are looking for is that the number "last" entered is greater than first. So why not begin the loop right away like this to reduce your code by almost half?:
// bring this outside of the loop so that it only shows once
System.out.println("Hello. I will calculate the sum");
System.out.println("of consecutive integers.");
// last and first are originally set equal to 0 so this loop will begin right away
while (last <= first) {    
     System.out.println("Please enter the starting number:");
     first = in.nextInt();
     System.out.println("Please enter the ending number:");
     last = in.nextInt();
    // add an if statement to print the please re-enter message
   if (last <= first) {
       System.out.println(last + " not larger than " + first);
       System.out.println("The ending number must be bigger than the first");
}Second,
The total part should not be in the loop. Notice how in your original code, the total was inside the loop so even if incorrect numbers were entered, the total would be displayed. The user would then be asked to enter new numbers and the total would be displayed again. I am assuming that the wanted behavior is to only display the total when correct numbers are entered. So we need to take the total out of the loop.
Third,
in your orignal code:
System.out.println("The sum of the numbers are " + total);
       total = sum(last, first);Here you are printing the value total before the total is calculated. That means that the value shown in the print will be incorrect. You must calculate the value of total before printing it.
I think this will get to the point where the code is almost what you are looking for.
Right now, your sum method simply adds the two numbers together, which could be done with a simple + sign, rather than writing a new method.
The for loop which I can see in your code looks like it will perform the action you are looking for.
What you need to do is move this for loop to the line just above the line where you are printing the total.
This means that the for loop will calculate the total, and then print it. If you print the total before calculating it you won't see the right value.
I hope this was clear and that it helped,
let me know if you have more questions and I will try to be more clear.