不是声明错误，非法启动类型

Question

import java.util.*;

public class ulang {

    public static void main(final String[] args) {
        int a;
        int b;
        int sum;

        Scanner scan = new Scanner(System.in);
        System.out.println("Enter num 1: ");
        a = in.nextLine();
        System.out.println("Enter num 2: ");
        b = in.nextLine();
        {
            sum = a + b;
        }

        for (i = 0; i < 5; i++) {
            (sum >= 10)
                System.out.println("Congratulations");
            else
                System.out.println("Sum of the number is Less than 10");
        }

    }
}

I'm weak on looping especially in Java. So I need some corrections on my coding, but I have no idea how to fix it.

The coding should run like this: User need to insert 2 numbers and the program will calculate the sum of both number. After that, the program will determine if the total of sum is >=10 or <10. If the sum >=10, "Congratulations" will appear but if it is <10, then "The sum of number less than 10" will appear. How to fix it?

Answer 1

This is the immediate problem:

(sum>=10)

I believe you meant that to be an if statement:

if (sum>=10)

Additionally:

• You're trying to use an in variable, but the Scanner variable is called scan
• Scanner.nextLine() returns a String - I suspect you wanted Scanner.nextInt()

• Your for loop uses a variable that hasn't been declared. You probably meant:

   for (int i = 0; i < 5; i++) 

A few other suggestions though:

• The sum isn't going to change between the loop iterations... why are you looping at all?
• You've got a new block in which you're calculating the sum, but for no obvious reason. Why?

• It's generally a good idea to declare variables at the point of initialization, eg

   Scanner scan = new Scanner(System.in); System.out.println("Enter num 1: "); int a = scan.nextInt(); System.out.println("Enter num 2: "); int b = scan.nextInt(); int sum = a + b; 

• Given that you want to take the same basic action (writing a message to the screen) whether or not the user was successful, you might consider using the conditional operator like this:

   String message = sum >= 10 ? "Congratulations" : "Sum of the number is Less than 10"; System.out.println(message); 

  That would then allow you to refactor the loop to only evaluate the condition once:

   String message = sum >= 10 ? "Congratulations" : "Sum of the number is Less than 10"; for (int i = 0; i < 5; i++) { System.out.println(message); } 

Answer 2

(sum>=10)

This line needs an if at the beginning, or it won't be read as a branch.

if (sum >= 10)

You also should name your main-class Ulang, because java class identifiers should start with an upper case letter, for readability.

The loop should look like the following:

for (int i = 0; i < 5; i++) {

The first part defines the counter and assigns zero to it. The second is your condition and the last counts for you.

Answer 3

for (int i = 0; i < 5; i++) {
    if (sum >= 10)
        System.out.println("Congratulations");
    else
        System.out.println("Sum of the number is Less than 10");
}