使用.toUpperCase（）编译代码时，获取“字符不能取消引用错误”；

Question

im new to java and am writing a program that will let you input your first and last name and will give you your initials, but i want the intitials to always be in upper case.

I get a "char cannot be dereferenced" error whenever i run the code.

    import java.util.*;

    public class InitialHere
    {
        public static void main (String[] args)
        {
            Scanner getInput = new Scanner (System.in);
            String firstName;
            String lastName;
            char firstInitial;
            char lastInitial;

            System.out.println("What is your first name?");
            System.out.println();
            firstName = getInput.nextLine();
            System.out.println();
            System.out.println("Thankyou, what is your last name?");
            System.out.println();
            lastName = getInput.nextLine();

            firstInitial = firstName.charAt(0);
            lastInitial = lastName.charAt(0);
            firstInitial = firstInitial.toUpperCase();
            lastInitial = lastInitial.toUpperCase();

            System.out.println();
            System.out.println("Your initials are " + firstInitial + "" + lastInitial + ".");

        }
    }

Answer 1

In Java, primitives have no methods, only their boxed types do. If you want to get the uppercase version of a char , the Character class has a method just for that: Character.toUpperCase :

 firstInitial = Character.toUpperCase(firstInitial);

(Do the same for lastInitial )

Answer 2

firstInitial is of type char which has no method toUpperCase . (Being a primitive, it has no methods at all.) Call toUpperCase on the original String instead.

Update (see comments): The documentation of Character.toUpperCase says:

In general, String.toUpperCase() should be used to map characters to uppercase. String case mapping methods have several benefits over Character case mapping methods. String case mapping methods can perform locale-sensitive mappings, context-sensitive mappings, and 1:M character mappings, whereas the Character case mapping methods cannot.

Therefore, the most robust approach would be to use

String firstName = firstName.trim();  // ignore leading white space
final String firstInitial = firstName.substring(0, firstName.offsetByCodePoints(0, 1)).toUpperCase();

Answer 3

Another solution:

firstInitial = (char) (firstInitial >= 97 && firstInitial <= 122 ? firstInitial - 32 : firstInitial);
lastInitial = (char) (lastInitial >= 97 && lastInitial <= 122 ? lastInitial - 32 : lastInitial);