Java: do-while loop with switch statement

Question

Language: Java

boolean x = false;
String letter = "NULL";

do{
    System.out.print("Enter grade (one character): ");
    letter = sc.next(); 
    switch (letter) {
       case "a": 
       x=true;
       break;
     case "A":
       x=true;
       break;      
     case "b":
       x=true;
       break;      
     case "B":
       x=true;
       break;      
     case "c":
       x=true;
       break;      
     case "C":
       x=true;
       break;      
     case "d":
       x=true;
       break;      
     case "D":
       x=true;
       break;
     case "f":
       x=true;
       break;      
     case "F":
       x=true;
       break;
     default:
       System.out.println("Invalid grade - must enter A,B,C,D,F (upper or lower case)");
       System.out.println(x);
       break;
     }
      System.out.println(x);
     }
      while(x=false);

--------------result output-----------------------------------result output--------------------------

Since I am new, I need a 10 reputation to post pictures of the output...so here is the output by typing it out...

//this is for if I enter String "e"

Enter grade (one character): e Invalid grade - must enter A,B,C,D,F (upper or lower case)

false

false

//this is for if I enter String "A"

Enter grade (one character): A

Invalid grade - must enter A,B,C,D,F (upper or lower case)

true

The question***:For my output,when I enter "e", I was hoping to see something like

Enter grade (one character): e

Invalid grade - must enter A,B,C,D,F (upper or lower case)

false

false

//loops through

Enter grade (one character):

So I was hoping that when I entered "e" it would make it false...and then start at the beginning until a result finally is entered that is: A,B,C,D,F (upper or lower case)

What is my mistake? I have been trying to brainstorm it myself, but I thought I would see what you guys have to say....

If you think the strategy I am using to get the output is not the best....What strategy/logic would you recommend?

Thanks for the help!

Solution 1

 while(x=false);

This is wrong. (should be ==)

Solution 2

Yes = is assignment operator you have to use == to check equality and other than that,note here your switch can be reduce to following and currently you have redundant code you can better use if statement with || operator here.

  switch (letter) {
     case "a": 
     case "A":    
     case "b":
     case "B":
     case "c":
     case "C":    
     case "d":   
     case "D":
     case "f":     
     case "F":
       x=true;
       break;
     default:
     //...

Solution 3

You can simplify the switch statement even further. By converting the letter to upper case you are checking for both upper and lower case. For example:

    do{
        System.out.print("Enter grade (one character): ");
        letter = sc.next(); 
        switch (letter.toUpperCase()) {
            case "A":                   
            case "B":       
            case "C":       
            case "D":       
            case "F":
                x=true;
                break;
            default:
                System.out.println("Invalid grade - must enter A,B,C,D,F (upper or lower case)");                    
                break;
        }                    
    } while(x==false);        

    System.out.println(x);