用字段Java创建一个类

Question

I'm trying to create a class that represents a person's name and that has fields representing the first name, middle initial, and last name, (also several methods).

When I try to run my code, I receive a Illegal modifier for the local class Name; only abstract or final is permitted Illegal modifier for the local class Name; only abstract or final is permitted error and cannot find a way to resolve this. Please help me resolve any errors so that my code will perform the desired (and commented) tasks. Thank you in advance.

public class Name {

    String first_name;
    String middle_initial;
    String last_name;

    //constructor that accepts first name, middle initial, and last name as parameters and initializes the Name object's state with those values
    public Name(String first_name, String middle_initial, String last_name) {
        first_name = "John";
        middle_initial = "Q.";
        last_name = "Public";
    }

    //method to return the person's name in first name, middle initial, and last name order.
    public String getNormalOrder() {
        String name = first_name + " " + middle_initial + " " + last_name;
        return name;    
    }

    //method to return the person's name in reversed order: last name, first name, and middle name.
    public String getReverseOrder() {
        String name = last_name + ", " + first_name + " " + middle_initial;
        return name;
    }

    //method to return the full name in first, middle, last order, in String form
    public String toString() {
        return first_name + " " + middle_initial + " " + last_name;
    }

    public static void main(String[] arg){
        first_name = "John";
        middle_initial = "Q.";
        last_name = "Public";

        getNormalOrder();
        getReverseOrder();
        toString();
    }

}

Answer 1

I suggest you start over with a file Name.java .

From the top, you can only have one public class of the same name as the file it is contained within.

public class Name {

}

Now, your field definitions are fine.

The constructor, however, should not hard-code the values of "John Q. Public", as this Name class can represent any instance of Name .

Therefore, you need to assign the fields using this , which is needed to "qualify" which variable you are using since they are the same variable names. (If you renamed String first_name here, to String fName , for example, then first_name = fName would be possible).

public Name(String first_name, String middle_initial, String last_name) {
    this.first_name = first_name;
    this.middle_initial = middle_initial;
    this.last_name = last_name;
}

Then, in the main method, you want to make an instance of this object.

Name name = new Name("John", "Q.", "Public");

That's it.

But if you want to display those values, simply calling your methods isn't correct, as it needs to know which Name value to call the methods on. You also need to print the String values that are returned to even see them.

System.out.println(name.getNormalOrder());
System.out.println(name); // calls name.toString()