使用 scanner 使用 if 语句初始化局部变量

问：

public class calGrades 
{
    public static void main(String[] args) 
    {
        int choice = 0;
        while(choice != 4)
        {
            int size; 
            Scanner sizeScanner = new Scanner(System.in);

            /* In the grades array, I get an error telling me that the local variable has not 
            yet been initialized. I want to initialize it using the scanner inside the if 
            statement*/ 
            int[] grades = new int[size]; 

            System.out.println("-----MENU-----");
            System.out.println("1) Enter size");
            System.out.println("2) Enter grades");
            System.out.println("3) Calculate average");
            System.out.println("4) Exit program.");

            Scanner choiceScanner = new Scanner(System.in);
            choice = choiceScanner.nextInt();

            if(choice == 1)
            {
                System.out.println("Enter size");
                sizeScanner = new Scanner(System.in);
                size = sizeScanner.nextInt();
            }
            if(choice == 2)
            {
                /*If i initialize size = 0, and then try the print statement 
                below, it will print out a 0 instead of whatever is read 
                into it via the scanner. */
                System.out.println(size)
                System.out.println("Enter grades: "); 
                Scanner gradeScanner = new Scanner(System.in);
                for(int i = 0; i < size; i++) //I get the same error here in my for loop.
                {
                    grades[i] = gradeScanner.nextInt();
                }
            }
        }
    }
}

我正在尝试在第一个“if”语句中初始化变量“size”。如果我在那里初始化变量，它不会改变大小的实际值。我知道它超出了范围，但我不知道如何让它存储在那里。这也给我的成绩数组带来了问题，因为我需要知道“size”的大小来设置数组的大小。我得到的错误是：局部变量大小可能尚未初始化 Java（536870963）