Java 错误：找不到符号符号：变量A

我正在尝试创建一种工资单，以便在控制台中打印，但我从代码中收到以下错误。它实际上只是一个错误很多次，但我认为我没有足够的java知识来修复它

import java.io.*;
import java.text.*;
import java.util.Scanner;

class Assign2num2 
{
  public static void main (String [] args)
  {
   String famname, firstname;
   double gross, deduct, tax, pay, hrs, ovtm;
   char letter, yn;
   Scanner in = new Scanner(System.in);
   System.out.println("Please enter your family name and first name.");
   famname = in.nextLine();
   firstname = in.nextLine();
System.out.println("Please enter how much you are paid per hour and the amount of hours you worked this week. Enter overtime hours seperately please.");
pay = in.nextInt();
 if (pay<0) {
  System.out.println("You must enter a positive number or zero for your hourly pay.");
    pay = in.nextInt();
 }
  else {
    pay = pay;
  }
hrs = in.nextInt();
 if (hrs<0||hrs>40) {
  System.out.println("You must enter a positive number less than or equal to 40, or zero for the amount of hours worked this week.");
    hrs = in.nextInt();
 }
  else {
    hrs = hrs;
  }
ovtm = in.nextInt();
 if (ovtm<0) {
  System.out.println("You must enter a positive number or zero for your overtime hours worked.");
    ovtm = in.nextInt();
 }
  else {
    ovtm = ovtm;
  }
   gross = (pay*hrs) + ((pay*2)*ovtm);
System.out.println("Please enter a letter indicating your tax category: A is no tax deduction, B is 10% of gross pay, \nC is 20% of gross pay, D is 29% of gross pay, E is 35% of gross pay");
letter = in.next().charAt(0);
 if (letter==A||letter==a){
  letter = letter;
  gross = gross;
 }
  else if (letter==B||letter==b){
  letter = letter;
  deduct = (gross*0.1);
  tax = gross - deduct;  
 }
  else if (letter==C||letter==c){
  letter = letter;
  deduct = (gross*0.2);
  tax = gross - deduct;
 }
  else if (letter==D||letter==d){
  letter = letter;
  deduct = (gross*0.29);
  tax = gross - deduct;
 }
  else if (letter==E||letter==e){
  letter = letter;
  deduct = (gross*0.35);
  tax = gross - deduct;
 }
  else {
    System.out.println("You must enter a letter between A and E.");
     letter = in.next().charAt(0);
 }

System.out.println("If you want $20.00 deducted from your weekly pay as a contribution to the \nUnited Way Charity, enter Y for yes. If not, enter N for no.");
yn = in.next().charAt(0);
if (letter==Y||letter==y||letter==N||letter==n){
  yn = yn;
 }
  else {
    System.out.println("You must enter either Y or N.");
    yn = in.next().charAt(0);
 }
  if (yn==Y||yn==y) {
    deduct = deduct + 20;
    tax = tax - 20;
  }
   else {
    deduct = deduct;
    tax = tax;
  System.out.println("PAY SLIP");
  System.out.println("---------");
  System.out.println(famname + ", " + firstname);
  System.out.println("---------");
  System.out.println("Gross Pay: " + gross);
  System.out.println("---------");
  System.out.println("Deductions: " + deduct);
  System.out.println("---------");
  System.out.println("Net Pay: " + tax);
  }
 }
}

16 errors found:
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 44]
Error: cannot find symbol
symbol:   variable A
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 44]
Error: cannot find symbol
symbol:   variable a
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 48]
Error: cannot find symbol
symbol:   variable B
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 48]
Error: cannot find symbol
symbol:   variable b
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 53]
Error: cannot find symbol
symbol:   variable C
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 53]
Error: cannot find symbol
symbol:   variable c
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 58]
Error: cannot find symbol
symbol:   variable D
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 58]
Error: cannot find symbol
symbol:   variable d
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 63]
Error: cannot find symbol
symbol:   variable E
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 63]
Error: cannot find symbol
symbol:   variable e
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 75]
Error: cannot find symbol
symbol:   variable Y
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 75]
Error: cannot find symbol
symbol:   variable y
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 75]
Error: cannot find symbol
symbol:   variable N
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 75] 
Error: cannot find symbol
symbol:   variable n
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 82]
Error: cannot find symbol
symbol:   variable Y
location: class Assign2num2
File: G:\Computer Science\Dr Java Exercises\Java Files\Assign2num2.java  [line: 82]
Error: cannot find symbol
symbol:   variable y
location: class Assign2num2

import java.io.*；
导入java.text.*；
导入java.util.Scanner；
类赋值2 num2
{
公共静态void main（字符串[]args）
{
字符串famname，firstname；
双倍总额、扣除额、税金、工资、工时、ovtm；
字符字母，yn；
扫描仪输入=新扫描仪（系统输入）；
System.out.println（“请输入您的姓和名”）；
famname=in.nextLine（）；
firstname=in.nextLine（）；
System.out.println（“请输入您每小时的工资和本周的工作时间。请分别输入加班时间。”）；
pay=in.nextInt（）；
如果（pay将变量与期望的字符进行比较时，该字符必须在单引号中，否则编译器会认为它是另一个未定义的变量

例如，改变

if (letter==A||letter==a){

到

您需要使用“”

if (letter == 'A')

字符文字必须用“”进行排序舍入，字符串文字必须用“”包围
使用字母=='D'，同样。字符文字用单引号括起来。
是的。你的信的其余部分也是一样。谢谢你！不过我以前没有使用过循环，但是当我运行这段代码时，我不希望它接受工作时间、工资/小时、加班时间等的负数。我有一个If语句检查这些，但如果在第二次询问后输入负数，则允许输入。算出它，但不允许。请格式化您的代码…他的字段“字母”定义为字符类型。
if (letter == 'A')