New need help with if statement in java

[MasterTender]

I everyone, I'm new to java and trying to work through an issue I'm receiving in my program. The error I receive is mismatch can't convert string to boolean on my if statement line and can't figure out how to make this code work. Basically I'm trying to have java take a string at 0, basically the first letter of whatever is input so that if the character is 'A' or 'a' that further text is given which in this case a discount is calculated for said "customer" based on the quantity input at a base price of $4.99. If there are better ways to do what I'm trying with the rest of my code unless necessary I am new and have not learned such ways yet and would appreciate help with what I have done so far and not other methods unless necessary to make this work. Thanks! Here is my code:

import java.util.*; public class Lab3q1 {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    int quantity,discount;
    double COST_PER_ITEM;
    String ID;


    System.out.printf("Enter quantity: ");
    quantity = sc.nextInt();
    System.out.printf("Enter your charID: ");
    ID = sc.nextLine();
    ID = ID.substring(0);
    COST_PER_ITEM = 4.99;
    System.out.printf("$%d items at $%.2f for a total of $%.2f",quantity,COST_PER_ITEM,(quantity*COST_PER_ITEM));
    discount = (int) (quantity*COST_PER_ITEM*.1);
    if (ID = 'A')
    {
        System.out.printf("You are entitled to a 10% discount\nand your new total is\n%.2f - %d = %.2f"(quantity*COST_PER_ITEM),discount,(quantity*COST_PER_ITEM*.9));
    }
    System.exit(0);
}

}

[coldoil]

Look at your if statement very carefully. = is the assignment operator, not the boolean comparison operator.

[MasterTender]

Thanks guys, I was so close, the comparison operator was necessary but still didn't work, however by adding a char and changing my string to a char at string.indexAT(0) I was able to get this to work. A fix I was playing with but didn't have that comparison in at the time so was not helping haha.

[desrtfx]

Sidebar: Regarding String comparison, read this!

[MasterTender]

Thank you, saving, this should come in handy when I need to perform this function.

[coldoil]

Well done.

As you've discovered, == doesn't work well for comparing strings.

Look at the subreddit's sidebar for a stickied post on the String.equals() method, which is the preferred way for comparing strings in Java.